Launching their own alternative Queen's speech, setting out the measures they believe ought to feature on Tuesday, Lib Dem Treasury spokesman Malcolm Bruce said his party would judge the real speech on "how it meets four historic challenges".

He said these were "modernising our antiquated constitution, reforming pensions, protecting the environment and preparing for successful membership of the single currency".

He said the Queen's speech, which sets out the government's legislative programme for the year ahead, would be judged "on its ability to deliver on issues which are vital for Britain's long-term future".

He added: "The way this government is going it will soon be standing room only in the long grass."

The Lib Dems' own Queen's speech would include bills on freedom of information, pensions reform, public transport and road traffic reduction, holding a referendum on electoral reform for Westminster, preparing for UK entry into the European single currency, and establishing a Food Standards Agency.

All of them are, in varying degrees, unlikely to appear in the government's real speech.

'Standing room only'

Earlier, Lib Dem leader Paddy Ashdown said the government should stick to its commitment to proportional representation (PR) for next year's Euro-elections and must "tackle the issue" of the single currency.

Mr Ashdown is under pressure within his own party over the closer links he has forged with the Labour government and Prime Minister Tony Blair.

Lib Dem MPs and grassroots members unhappy at the closer links have protested at what they see as Mr Ashdown's failure to win any significant advance for the party's own policy priorities - PR , freedom of information and other constitutional reforms - from his membership of a joint cabinet committee.