Gordon Brown said on Wednesday the world’s leading economies were close to agreeing a global bank tax, amid hopes in Downing Street that a deal can be concluded at the G20 summit in Canada in June.

Mr Brown believes that opinion has shifted decisively in favour of a globally co-ordinated tax after President Barack Obama’s move last month to raise $90bn (£57.7bn) from a US bank levy.

The tax could cost the financial services sector tens of billions of pounds a year.

The prime minister has strongly advocated some kind of charge on banks. “I’m interested in the way support is building up for international action,” he said in an interview with the Financial Times.

Last year, Mr Brown mooted a tax on bank transactions – a so-called Tobin tax – as one of a number of options to make sure the “contribution banks make to society is properly captured”.

The US immediately shot down that option, but the International Monetary Fund has been looking at other ideas.

Mr Brown believes that the IMF will endorse a global bank levy before its April meeting in Washington.

Downing Street hopes an agreement in principle can then be agreed by world leaders at the G20 summit in June, although the implementation of the levy and the detail of how it would work could take longer.

“People are now prepared to consider the best mechanism by which a levy could be raised,” Mr Brown said.

He thought the IMF would propose a method that would be “somewhat different” from the tax on wholesale funding proposed by Mr Obama.

Other options would be for a tax on bank profits, turnover or remuneration. But the IMF is expected to shy away from branding the levy as “an insurance scheme” because doing so might encourage banks to think they would automatically be covered by the taxpayer if they ran into trouble again.

Mr Brown insisted he was not attacking banks or their wealthy employees for ideological reasons. On the new 50p top rate of tax, he said: “We didn’t want to raise the top rate of tax.” He added: “We have no desire to have a tax rate that is higher than necessary.”

The prime minister said those with the “broadest shoulders” should pay more, and insisted that the tax would raise “a substantial amount of additional money”. He admitted: “It’s not as high as you would like it to be because of avoidance.”

In a wide-ranging interview, Mr Brown appeared focused on economic summits that will take place after the expected May 6 election, confirming the impression of aides that he still believes he can overturn a 10-point poll deficit.

He confirmed there would be a Budget before the election and insisted there was “no disagreement” with Alistair Darling, chancellor, on the pace of cutting the £178bn deficit: the plan is to halve borrowing over four years.

The prime minister again suggested that Mr Darling might be able to increase planned spending in some areas, if debt interest and benefit spending were lower than expected, or growth higher.

“If anything, we’ve shown ourselves to be better than people expected in most of these areas,” he said.

“That leaves the chancellor free to make decisions that he will make at the time of the Budget.”

Former Barack Obama supporter Jim Cramer on Friday said the stock market would have a huge rally if Scott Brown defeats Martha Coakley in Tuesday’s special senatorial election in Massachusetts.

“I think investors who are nervous about the dictatorship of the Pelosi proletariat will feel at ease, and we could have a gigantic rally off a Coakley loss and a Brown win,” said Cramer on Friday’s “Mad Money.”

“It will be a signal that a more pro-business, less pro-labor government could be in front of us.”

The often outspoken CNBCer marvelously declared it a “Pelosi politburo emasculation” (video embedded below the fold with partial transcript):

JIM CRAMER, MAD MONEY HOST: We know it’s earnings season. You can no more avoid it than you could avoid getting your report card or worse – your parents getting your report card. You saw that today when people sold the market on allegedly weak earnings from Intel and JP Morgan, emphasis on allegedly. The Dow getting hurt bad, down a hundred big ones. S&P giving back more than a percent. But that doesn’t mean that the most important factor in next week’s game plan is an earnings report. Far from it. Come with me. The number you need to watch is the number that Scott Brown racks up against Martha Coakley in this amazing Massachusetts Senate race. I say amazing ’cause this was supposed to be a walkover. I mean, even a few weeks ago it was a lock for Democrat Coakley. But now everything’s up in the air, and a Brown win would be devastating for the president’s agenda. Let’s put Brown, okay, and I don’t mean UPS which I happen to own for my charitable trust. Particularly on healthcare reform, because Republican Brown has said he will definitely vote against the plan.

Brown in the Senate? That wrecks the 60-vote supermajority the Democrats have been counting on. It could spell the end for this almost year-long nightmare of a piece of healthcare legislation.

What does a Brown election mean larger than this? Well, first you’re going to get a knee-jerk rally in all the so-called penalized stocks — the HMOs, the drugs, the medical device-makers. I call it “knee-jerk,” though, because these stocks have been on fire for months. Look at Cramer fave WellPoint, or United Health. 52 week high. 52 week high. Merck, 52 week high. It’s been clear as a bell that the healthcare reform wasn’t going to affect most healthcare stocks. That’s versus what we thought last year.

More important, though, I think investors who are nervous about the dictatorship of the Pelosi proletariat will feel at ease, and we could have a gigantic rally off a Coakley loss and a Brown win. It will be a signal that a more pro-business, less pro-labor government could be in front of us. Hey, would you say it is more China like perhaps? No, we can never be as capitalist as the Communist Chinese. But how about a little bit less like the old Soviet Union? Yeah, that would be a bit more like it. Pelosi politburo emasculation! Everything from the banks, which are usually in the Democrats’ penalty box, or the oils which are despised by this administration for being carbon, could be propelled dramatically higher all of this Tuesday night. Delicious. Absolutely delicious!