The Liberal Democrats will have to convince voters their manifesto commitments are "credible" before the next general election, a senior LibDem has admitted.

Education minister David Laws said the party would have to be clear about its priorities ahead of potential Coalition negotiations.

LibDem delegates will start the process of hammering out their next manifesto at their annual conference in Glasgow this weekend. The party is still struggling to draw a line under accusations they betrayed voters with their 2010 U-turn on tuition fees.

This time last year leader Nick Clegg was forced to release a much-mocked video apology for the move.

Senior LibDem sources told The Herald there will be no "rerun" of the tuition fees debacle if the party goes into coalition into 2015.

Admitting that there were issues following the negotiation process last time around, Mr Laws said there would be "thoughtful discussions about the way in which we present our policies next time so that the electorate can see that they are credible and deliverable".

But he said it was "too soon" for the party to produce a list of non-negotiable or "red line" issues.

"Until we have that opportunity to have a debate, to identify the policies that the party is committing itself to in principle, we can't then have a sensible debate about trading off different competing priorities."

Those decisions would not be made until the "second half of 2014" he saidstressing that other parties would also face having to give up policies if the election did result in another coalition government.