The threatened action comes as Midland's parent, HSBC Holdings, prepares to announce a leap in profits. Figures due today are expected to show half-year pre-tax profits up by about 15 per cent to more than pounds 1.35bn. Midland's own pre-tax profits are forecast at about pounds 300m.
The union, which has rejected a 2.25 per cent pay offer, has begun balloting clerical staff. It has set a deadline of 26 August for voting to be completed, and said any strike action would be likely to start in September.
'Staff at Midland have lived through lean years but now they want their promised share of the better times,' the union's negotiating officer, Bernadette Fisher, said.
'Fortunes are being made in Midland but the staff only get a 2.25 per cent share. This is corporate greed of staggering proportions. Large profits are being generated, but at the expense of staff salaries.'
Like the rest of the UK banks, HSBC is expected to show flat lending growth when it reports its six-monthly figures today.
Provisions against bad debts are expected to fall, while high inflation in Hong Kong will probably drive up costs, according to analysts.
Dealing profits are expected to be a problem area following market turbulence in February. There have been strong rumours in the City that Midland Global Markets had an especially difficult February/March.