The leader of the Liberal Democrats is to promise a political partnership to carry out the task in spite of the fact the Government is stalling over the appointment of a commission on electoral reform for Westminster.
In a speech on Tuesday Mr Ashdown will argue there is a "great project in hand", adding: "It will take 10 years to complete. It is nothing less than the modernisation of Britain. The Liberal Democrats and New Labour are natural partners in that project."
Mr Ashdown's pledge comes at a sensitive time in relations between the two parties, with the formal establishment of the commission - likely to be headed by Lord Jenkins of Hillhead - delayed for at least two weeks.
Lord Jenkins' chairmanship has been held up because its terms of reference have yet to be agreed.
One Liberal Democrat source said that a deal was "days or weeks away", but a Labour insider said that the issue was not on the Government's immediate "radar screen".
The committee, whose findings will go to a referendum, is likely to be announced after a meeting of the Lib-Lab Cabinet sub-committee.
The dispute concerns the inclusion of the Alternative Vote system - under which second-preference votes can be re-distributed - in the commission's remit. Some Labour modernisers favour the system which the Liberal Democrats argue is not a proportional one.Reuse content