His call came as the LibDems continued to reel from the backlash over tuition fees in England.
In an interview with The Herald, Gordon MP Malcolm Bruce said he felt they had been punished "disproportionately" for that decision.
The veteran MP also accused critics of his appointment, at the height of a damaging row over allegations of sexual harassment against former party chief executive Lord Rennard, of both sexism and ageism.
He said his message to voters was: "If you like the look of what we have to say don't back us into a corner and insist that we make pledges.
"Just recognise what our priorities are, and if you like them vote for them, and then we will be in a position to implement them."
Labour said "the LibDems don't want to make pledges because they can't be trusted to keep them".
Accusations of betrayal have dogged the party since it abandoned its opposition to increased university tuition fees in England to enter coalition government with the Conservatives.
Mr Bruce said that in his view the electorate was "punishing us disproportionately" for that policy.
"For someone like me who has been a Liberal for 50 years the idea that all I ever wanted was a short-cut to power is frankly laughable," he added.
The LibDems plan to fight the next election by "digging in", a strategy it hopes will allow it to save many of the seats it already holds.
Mr Bruce said he thought voters would lose out if there was not another Coalition with his party next time around.
"If they vote the LibDems down and out at the next election, I'm pretty sure that people will wish that they hadn't," he said.
His supporters say the fact the Gordon MP has already announced he will not stand again in 2015 make him an asset in the campaign, able to tour the television and radio studios while other MPs fight to keep their seats.