LONDON (Reuters) - Britain’s top companies face a red warning if they don’t have more than one woman on their board, the Investment Association said on Thursday, adding to pressure for more female representation at top levels of management.

FILE PHOTO: People cast long shadows in the winter sunlight as they walk across a plaza in the Canary Wharf financial district of London, Britain, January 17, 2018. REUTERS/Dylan Martinez/File Photo

The body which represents big asset managers said it was expanding its traffic light system which guides big investors on whether a company is complying with best practice in areas of governance such as executive pay.

The IA said it would apply a red alert to a top 350 listed company if there are none or only one woman on the board

Ratings on all aspects of a company’s governance are done three weeks before its annual shareholders’ meeting. Currently there are no red tops related to the number of women on boards, but some are expected, an IA spokesman said, without giving any further detail.

A red top represents the highest level of warning and is reserved for companies where shareholders should have the most serious concerns, the IA said, though it has no formal power over how investors vote on company policies.

An amber top would be applied where there is more than one woman, but less than 25 percent of the board are women.

Repeated calls for more women on boards have been made in recent years and in 2011 for instance a government report said companies in the FTSE 100 should aim for at least 25 percent female board member representation by 2015, yet progress has been slow.

At the highest chief executive level a study released in 2018 on International Women’s Day found women CEOs in the FTSE 100 were outnumbered by chiefs called David.

The IA also said it was making its grading of company pension arrangements for executives more stringent.

A company will be “red topped” if it does not explicitly state that any new executive director will have their pension contributions set in line with the majority of the workforce.

The aim is to stop pensions being used as a mechanism for increasing total pay.