NICK Clegg will today tell his critics there is no turning back the clock to when the Liberal Democrats enjoyed the comfort of opposition, and they should accept the hard new reality of being in government or support someone else.

In a tough, uncompromising message to the party's annual conference in Brighton, the leader will insist the country's "sacrifices of austerity" will bring the "rewards of shared prosperity"

However, another poll has shown public trust in the Deputy Prime Minister has plummeted.

The latest Comres survey last night said Mr Clegg was the least trusted leading politician to see the country through the downturn, with a net trust score of -49%. David Cameron was placed on -16%, Ed Miliband -36%, George Osborne -39% and Ed Balls -43%.

Some 76% of people said the LibDem leader was right to apologise for breaking his pledge not to raise tuition fees, but 66% felt his apology was insincere and made for political reasons.

Mr Clegg – buoyed earlier in the week when conference overwhelmingly voted to support the Coalition's deficit-reduction plan – will this afternoon say the dissenters claimed the LibDems were incapable of making the transition from opposition to government, saying the choices would be too sharp and the decisions too hard.

"Two years on, the critics have been confounded. Our mettle has been tested in the toughest of circumstances and we haven't been found wanting," he will insist.

Addressing his critics directly, Mr Clegg will say: "I know there are some in the party – some in this hall even – who, faced with several years of spending restraint, would rather turn back than press on; break our deal with the Conservatives, give up on the Coalition and present ourselves to the electorate in 2015 as a party unchanged.

"It's an alluring prospect in some ways. Gone would be the difficult choices, the hard decisions, the necessary compromises. And gone too would be the vitriol and abuse, from right and left, as we work every day to keep this Government anchored to the centre ground."

Mr Clegg will declare: "But conference I tell you this: The choice between the party we were and the party we are becoming is a false one.

"The past is gone and it isn't coming back. If voters want a party of opposition – a 'stop the world I want to get off' party – they've got plenty of options, but we are not one of them. There's a better, more meaningful future waiting for us, not as the third party but as one of three parties of government."

The party leader will speak of investing in young people and the "Liberal promise", which is "the freedom to be who you are, the opportunity to be who you could be".

He will announce an extra £500 for every child who leaves primary school in England below the expected level in Maths and English; a cost this year of £50 mil-lion, with the money coming from departmental underspends.

In a separate development yesterday, Mr Clegg held out the prospect that beyond 2015 his party would recommend cutting age-related benefits such as free television licences, free bus passes and the winter fuel allowance for better-off pensioners.

Stressing there would be no such benefit cuts in this parliament because they are ruled out by the Coalition Agreement, Mr Clegg said "for the future" it would be very difficult to explain why someone poor could lose housing benefits while at the same time the billionaire tycoon Lord Sugar should receive a free bus pass.

He said some rich people would be willing to "give up universal entitlements to help people less lucky than them to make ends meet".

Earlier, LibDem Minister Don Foster said he should not be getting the annual £200 winter fuel payment when the less well-off in society were "having it really tough".

While Mr Clegg again stressed he wanted to see the better-off pay their fair share through a mansion tax, he recognised there would be more cuts after 2015.