Santander is reported to have made a renewed bid for the Williams & Glyn network which Royal Bank of Scotland is struggling to dispose of to meet an EU deadline.

The English business with more than 300 branches and 1.7million customers was due to be rebranded under the Williams & Glyn name next year.

But RBS chief executive Ross McEwan, whose warnings about the difficulty of the separation project have become ever graver, has said it is the world’s most complex banking IT project.

The disposal was ordered by the European Commission in approving RBS’s £45.5bn taxpayer bailout in 2008.

After an earlier Santander deal collapsed in 2012 due to IT issues, RBS began planning for a £2bn stock market flotation, only to renew talks with trade buyers this year as listing prospects faded.

The deadline for the deal is supposed to be the end of 2016 but the bank has already said it is unlikely to meet it.

Now Santander is said to have tabled a fresh proposal in the past few days., which the Treasury reported to have been informed.

Neither bank would comment on the speculation.

Any positive news would help to lift the potential gloom over the bank’s half-year results on Friday, with banking stress test worries weighing on the shares this week – they were down another 1.7per cent yesterday.

The bank’s most recent warning was that “due to the complexities of Williams & Glyn’s customer and product mix, the programme to create a cloned banking platform continues to be very challenging and the timetable to achieve separation is uncertain”.

As a standalone, W&G would rank as the UK’s seventh-largest bank, with around two per cent of personal current accounts market and five per cent of the SME market.