A Transport for London spokesperson said:

"Both the Mayor and the direct employers, the Administrator and Metronet, have given the trades unions clear written assurances that meet all of their concerns, namely that there will be no job cuts or transfers as a result of the collapse of Metronet and no loss of pensions now or at any time in the future.

"London Underground, Metronet, the Administrator and ACAS all yesterday asked Bob Crow what further assurances the RMT is seeking.  There has been no response.

"We are still prepared to meet any reasonable requests to meet first thing or throughout today, as it is clearly unreasonable to proceed with a strike when all of the trades unions' concerns have been met, and without the RMT informing us what they seek to achieve."