The Liberal Democrats have claimed that high taxes for top-earners will not stop Conservative voters defecting to the party in the forthcoming general election.

In an interview with the Guardian Mark Oaten, the Lib Dem home affairs spokesman, also said the party must show voters they can trump their rivals' law and order policies by proving that Labour and Tory rhetoric masks a failure to curb crime.

He admitted that accepting Labour's plans for control orders to tackle terrorism was "not a popular decision" with all party members.

"There will be some cases where you cannot prosecute," he said. "As a mature party - a sensible party - we cannot just walk away from it."

Meanwhile, party leader Charles Kennedy tells the FT that the erosion of trust in Tony Blair will make it more difficult for him to campaign for a European constitution after the election.