Labour is finished and only we can deliver a fairer Britain, says Clegg

Nick Clegg declared Labour was "finished" as a political force and insisted that the Liberal Democrats had replaced it as the natural party of "social justice", in his first speech to the party's annual conference.

The Liberal Democrat leader set his sights on capturing dozens of Labour seats at the next election following mass defections by disillusioned former supporters of the Government. The party has drawn up a hit list of more than 50 Labour constituencies – from the south coast to Aberdeen – that it believes it can win. An internal memo obtained by The Independent shows it is optimistic about gaining a swathe of seats in Labour's heartlands in the North and Midlands.

Closing the conference, Mr Clegg claimed the political map had transformed over the past year as the credit crunch hit Britain, Gordon Brown's popularity collapsed and Labour descended into civil war. And although his party is becalmed in the polls at around 17 per cent, Mr Clegg insisted the Liberal Democrats were well placed to capitalise on government woes. He said: "Labour is finished, it's over. The Liberal Democrats are now the only party that can deliver social justice, the only choice for anyone who wants a fairer Britain. If you were drawn to Labour in the 1990s because you believed in a better future, because you were filled with hope that things would get better, join us. We are the ones who can make it happen."

Mr Clegg, who has been accused by critics of tacking to the right after winning backing for his plans to cut taxes and trim government spending, also delivered a searing critique of the Tories under David Cameron.

He said: "Cameron's only aim was to make the Conservatives inoffensive. Problem is, once you strip out the offensive parts of the Conservative Party there isn't much left. Cameron's hope is to become the Andrex puppy of British politics – a cuddly symbol, perhaps, but fundamentally irrelevant to the product he's promoting."

Mr Clegg said the party was growing in strength and predicted it would take "a giant leap" at the next election towards his ambition of doubling the number of Liberal Democrat MPs in the next decade. In an echo of David Steel's infamous appeal to the party in 1981 to "go back to your constituencies and prepare for government", Mr Clegg told the conference: "I can't tell you every step on the road for us as a party. But I can tell you where we're headed – government."

He dispensed with a podium for his first address as leader to the party's annual conference and walked around the platform as he delivered his 38-minute speech, much in the style of Mr Cameron at last autumn's Tory conference.

Concentrating on domestic issues, Mr Clegg set out a four-point economic recovery plan to "get Britain out of this mess".

He called for more help for families about to lose their homes, an end to the "freewheeling bonus-driven short-termism of the City", interest rates to be pegged to house prices and tax cuts for low- and middle-earners. Mr Clegg said: "What hard-up families need most of all today is food on the table, petrol in the car and warmth in their homes."

The Liberal Democrats, who hold 63 seats at Westminster, are targeting London boroughs such as Camden, Brent, Islington, Lambeth and Haringey, Midlands towns and cities including Northampton, Derby and Birmingham, as well as northern Labour strongholds such as Liverpool, Newcastle and Sheffield, where the Liberal Democrats run local councils.

They have high hopes for the Welsh valleys and for Edinburgh, Glasgow and Aberdeen. Party officials are also considering turning their fire on seats where long-serving Labour MPs may stand down, repeating a strategy of seizing ex-Tory fiefdoms that delivered gains in the west of England.

The Liberal Democrats are second to Labour in 107 seats. Twelve are winnable on a swing of 5 per cent or less and 32 would fall on a swing of up to 10 per cent. Strategists believe voters are so disillusioned with Labour that Tory supporters will vote tactically to throw out Labour MPs.

Labour MPs on the Lib Dems' hit list

Charles Clarke, Norwich South

The former home secretary's outburst against the Prime Minister sparked the latest round of Labour infighting. With a 3,653,majority, he is No 9 on the Lib Dems' list.

Phil Woolas, Oldham East and Saddleworth

Environment minister spearheading the Government's response to climate change. He has a majority of 3,590, and is No 13 on the list.

Andrew Smith, Oxford East

Former work and pensions secretary sitting on a majority of just 963. His seat is the Lib Dems' top target, winnable with a swing of 0.37%.

Nigel Griffiths, Edinburgh South

Former trade minister and former deputy leader of the Commons, with a majority of just 405. The No 2 Lib Dem target, his seat would be captured with a swing of 0.48%.

Claire Ward, Watford

Once the youngest MP in the Commons, and the archetypal "Blair Babe". Currently a government whip, with a majority of just 1,148.

Jane Kennedy, Liverpool Wavertree

Financial Secretary to the Treasury, but has been a minister in several departments. Has a majority of 5,173 and is No 12 on the hit list.