The City watchdog has ordered banks to put an end to their bonus culture, in a report that blames staff incentives for corrupting the services they provide and leading to millions of consumers being missold investments and insurance policies.

Many if not all of the recent mis-selling scandals over products including payment protection insurance (PPI), endowments and pensions had come about because of the way companies rewarded sales rather than service, the FSA said.

The watchdog investigated the incentive and bonus schemes at 22 financial firms, and uncovered a range of "serious failings".

It is understood that the worst were at Lloyds Banking Group, which has been referred to the FSA's enforcement division. This could result in the group, which is 40% owned by the government, facing a fine of billions of pounds. Lloyds has already set aside more than £3.5bn to cover compensation payments.

Martin Wheatley, the FSA's managing director, said banks used to be a place "where you would go in, stand in a queue and have a pleasant chat with the clerk", but some time ago financial institutions had changed their view of consumers "from someone to serve to someone to sell to".

The FSA has ordered firms to drop such sales tactics in favour of schemes that put the customer first, and said bank bosses should "take a real interest in fixing this". If firms failed to comply, the watchdog said, it was prepared to introduce new rules cracking down on bonus schemes that prioritise sales.

"What we found is not pretty," Wheatley said. "Most of the incentive schemes we looked at were likely to drive people to mis-sell in order to meet targets and receive a bonus, and these risks were not being properly managed."

He said he had ruled out getting rid of incentive schemes altogether, but banks would be expected to properly consider whether their incentive schemes increased the risk of mis-selling.

"I want to draw a line in the sand and use the report we are publishing today to set out our expectations," he said. "CEO's are ultimately accountable for the way their staff are incentivised, so we expect them to take a real interest in fixing this."

Where a recurring problem was identified, banks would be expected to investigate, take action and pay compensation, the FSA said. In the past, incidents of misselling have often been left to the watchdog and consumer bodies to identify and act upon.

Firms have until the end of October to submit their views on the guidance, and Wheatley said he expected them to start to clean up their act immediately.

Lloyds would not confirm whether it had been referred to the FSA's enforcement division, but said in a statement that it had made "significant changes" to its incentive schemes since the beginning of the year. It said it had been " working closely with [the FSA], keeping them updated on our progress and to ensure the changes we have made to the schemes are appropriate."

Richard Lloyd, the Which? executive director, said that the FSA's findings supported his organisation's view that most banks had incentive schemes that prioritised sales.

"This must change. It is clear that the light touch regulation of the past has not worked. We want to see the FSA rigorously enforcing the rules and taking tough action against those banks that continue to let their customers down," he said.

Figures released by the banks last week showed that customer complaints soared in the first half of this year, due to increasing numbers of cases relating to the mis-selling of PPI. Lloyds received around 860,000 complaints in the first six months, a 145% increase on a year ago. Complaints to NatWest doubled year-on-year, while those to Barclays rose by 80%.