The deadline for the Spanish-led consortium to make a formal offer for National Express, the UK bus and rail operator, is to be extended for a second time so that due diligence can be completed.

The Spanish Cosmen family, which owns 18.6 per cent of the group, and private equity firm CVC had until Friday to complete the process and either make a 500p-a-share offer or walk away but the Takeover Panel is expected to give the companies a further two weeks to assess the financial health of the company.