Lloyds Bank has a capital shortfall of 8.6 billion pounds, Britain's banking regulator said on Thursday, a day after the UK government signaled plans to return the part-state owned lender to the private sector.

The Prudential Regulation Authority said the aggregate capital shortfall at UK five banks at the end of 2012 was 27.1 billion pounds, slightly higher than its 25 billion initial estimate in March this year.

In March, the banks had plans to raise 12.5 billion pounds during this year, and the PRA raised this estimate to 13.7 billion on Thursday.

Banks are required to have a core capital buffer equivalent to 7 percent of their risk-weighted assets by December.

RBS had a total shortfall of 13.6 billion pounds, Lloyds 8.6 billion pounds and Barclays 3 billion pounds at the end of 2012, the PRA said.

The Co-op had a shortfall of 1.5 billion pounds and Nationwide 400 million pounds. There were no shortfalls at HSBC and Standard Chartered , the watchdog, part of the Bank of England said.

The banks have already begun announcing steps to plug the shortfalls and combined, they will generate 13.4 billion of capital, the PRA said.

"A number of these intended actions will require regulatory approval before being implemented. As such, they cannot be assumed to have contributed to meeting the requirement until approval is given," the PRA said.

"In the event that they are either not carried out or fail to be approved, other actions will be required of those firms in order to reach the specified standard."

The PRA said it has given some flexibility by allowing some banks to complete actions during the first half of 2014.

After the actions planned so far, four banks will still have a shortfall and they have been required to submit plans for additional actions.

(Reporting by Huw Jones, editing by Matt Scuffham)