Liberal Democrats who are setting their sights on forming a future coalition with Labour pose a "profoundly dangerous" threat to the party's identity, a senior MP has warned.

In a thinly veiled warning to Vince Cable, who makes little secret of his interest in working with Labour, Sir Malcolm Bruce says it is "naive, misguided and dangerous" to assume the future of the Lib Dems lies with Labour.

Writing in the Guardian, the veteran Lib Dem MP says: "Working for a coalition with Labour is profoundly dangerous for our party's identity. Now we have gone from a party of perpetual opposition to a party of government, we have to present ourselves differently to voters. We must make clear that we are an independent party with a distinctive set of values and political approach."

Bruce, MP for the Aberdeenshire seat of Gordon since 1983, is speaking out amid concerns at senior levels of his party that Cable is working to undermine Nick Clegg to pave the way for a coalition with Labour after the next election. Lord Oakeshott of Seagrove Bay, a Cable ally, recently called for a change in Lib Dem "strategy and management".

Clegg's allies have dubbed Cable and Oakeshott the "Continuity SDP" – former members of the Labour party who joined the SDP and who would feel more comfortable in coalition with their old party. Sir Menzies Campbell, the former leader who hails from the Liberal side of the old SDP/Liberal Alliance, recently criticised Cable for texting Ed Miliband.

In his Guardian article, Bruce says the Lib Dems would be making a major mistake if they focused solely on Labour. "To assume, as some people clearly do, that we should now be aiming to lay the groundwork for a future Labour/Liberal Democrat coalition is naive, misguided and dangerous for the future identity of the party. It is naive because we cannot predict the outcome of the next election – that will be decided by millions of voters making individual decisions according to a range of local and national considerations. It is misguided because it assumes that Liberal Democrat supporters and potential Liberal Democrats voters have a homogeneous view of the party."

Bruce launches a powerful critique of Labour and the Tories to show that the Lib Dems should remain apart from both parties. This approach, which used to be called "equidistance", was abandoned by Paddy Ashdown when he embarked on coalition negotiations with Tony Blair in the runup to the 1997 election.

Bruce writes: "Labour is as divided between New and Old Labour as the Conservatives are between one nation and ultra-conservative Tories. The vested interest and prejudice that characterises Conservatives are negative reasons why I am a Liberal Democrat."

But Bruce is particularly critical of Labour. "Socialism is illiberal – it subordinates the individual to the collective. They have ridden roughshod over our hard won civil liberties.

"The desultory talks that took place with Labour before the present coalition was agreed revealed arrogant contempt for Liberal Democrats and a belief that our job was to keep Labour in power and not rock the boat. The vitriol that has been heaped on the Liberal Democrats by Labour during the first half of this parliament will not easily be discounted or forgotten."

Bruce insists that Lib Dems should be prepared to explain to former supporters who were bitterly disappointed when the party formed a coalition with the Tories. "Those people were ill-prepared for an outcome that led to the current coalition, even though the leadership made it crystal clear we would first seek to work with the largest party in the event of no one winning outright. Simplistically, for those people, the main thing wrong with the present arrangement is that we are in coalition with the 'wrong' party."