Millionaire ministers said yesterday that they may curtail trade union rights even further after Grangemouth bosses took offence at "unpleasant" protests against job cuts last month.

Union officials slammed the government after the Con-Dem coalition announced a review into activists' tactics.

Cabinet Office Minister Maude said he had asked barrister Bruce Carr to look into the Unite union's "leverage" strategy, which saw protests at billionaire Ineos boss Jim Ratcliffe's Limewood Hotel and the Lymington Town sailing club where Mr Ratcliffe - owner of the £130 million Hampshire II superyacht - is a member.

The panel - to be made up of Mr Carr, a bosses' representative, and a "union representative" - is expected to publish its report late next year.

The Unite union called it "nothing more than election stunt" while GMB leader Paul Kenny branded it a transparent attempt to divert attention from the real problems Britain faces.

Millionaire Mr Maude appeared to blame Unite for the Grangemouth refinery's week-long shutdown.

The Ineos-owned complex on the Firth of Forth is the biggest industrial site north of the border, processing two-thirds of the petrol in Scotland's forecourts.

Management powered-down the entire plant last month against Unite's advice and locked out more than 1,000 workers, demanding they submit to drastic cuts to pay, pensions and terms of employment or be out of a job altogether.

Mr Maude said subsequent allegations of "quite unpleasant" behaviour towards scabs and managers demanded an inquiry.

But Mr Kenny said the "real scandal at Grangemouth" was "how could one man - a non-resident at that - be able with impunity to hold the country to ransom by having the unfettered power to shut down a facility vital to the wellbeing of the nation and the economy of Scotland?"

"At a time when living standards are falling, when people are struggling to pay energy bills, when executive pay is rocketing and when investment in industry by cash-rich employers has fallen through the floor, this announcement seems like another sop to the Tory backbenches," said Mr Kenny.

A Unite spokesman urged other trade unions not to collaborate with the coalition's review.

And TUC general secretary Frances O'Grady said: "This has nothing to do with good industrial relations and is simply part of the Conservative Party's general election campaign.

"We already have some of the most restrictive union laws in the democratic world.

"Too many Conservatives seem to think that cheap anti-union jibes will detract from the cost of living crisis.

"The polls suggest they are wrong."