HSBC bank is considering spinning off its UK retail unit in a £20bn (€28bn, $30.4bn) deal, as the bank reviews whether it should move its headquarters out of Britain.

The Sunday Times, citing senior sources, reported that HSBC may spin off its UK division and revive the old Midland Bank.

Britain's largest bank is reviewing whether to move its headquarters to Asia amid rising operational costs and tougher regulations at home. The bank considers its former home Hong Kong among other Asian destinations. The move would threaten London's reputation as a global hub for finance and investment.

"As part of the broader strategic review taking place, the board has therefore now asked management to commence work to look at where the best place is for HSBC to be headquartered in this new environment," HSBC chairman Douglas Flint confirmed earlier.

"The question is a complex one and it is too soon to say how long this will take or what the conclusion will be, but the work is under way."

The bank's decision may also have prompted by a UK law that forces banks to separate their retail operations by 2019.

The Sunday Times added that the spin-off could speed up HSBC's exit from the country, as the UK is scheduled to hold its general election on 7 May.

Shares of HSBC climbed 4.8% earlier in Hong Kong on 27 April, following a 4.2% jump on 24 April. HSBC was founded in 1865 in Hong Kong and Shanghai, and later it moved its headquarters from Hong Kong to London in 1993 after taking over Midland Bank in the UK.

Midland had been part of the FTSE 100 index, and offered business support and capital banking to leading merchants and manufacturers.