An investor at Canary Wharf -based HSBC claims it would back the bank if it left the UK.
Relocation is a possibility due to increasing pressure from regulators on lenders, said head of equities at Standard Life, David Cumming.
The investor holds a 1.06% stake in HSBC and is its 12th biggest shareholder.
Cumming told the BBC Radio 4 Today programme, reported in The Telegraph , regulators continually “moving the goalposts” meant the Canada Square bank was “very, very close to losing patience.”
He said: “Given the situation, where there is no clear end point in terms of ever increasing capital requirements, and the fact that they are being put at a competitive disadvantage, and the fact that we will see better growth, earnings and dividend prospects unless the regulator changes tack then logically we would be supportive of a move if they chose to do that.”
The bank is due to make a decision at the end of the year.
It has previously considered re-locating to America and Hong Kong.