(Reuters) - Deputy Prime Minister Nick Clegg wrote to his Liberal Democrat legislators on Wednesday in a bid to head off a threatened rebellion over plans to double university charges for students.

The plans in a government-ordered review have caused tensions in Clegg's party and could lead to a parliamentary defeat if enough Liberal Democrat legislators rebel.

The divisions were not expected to bring down the coalition of Conservatives and Liberal Democrats, but add to uncertainty over whether it can hold together for a full five-year term.

The government on Tuesday backed the proposals to remove a cap of 3,290 pounds a year that universities are allowed to charge students for their tuition, and take Britain closer to a U.S.-style fees model.