According to an analysis by the BBC, four in ten companies that are required by law to carry out an annual gender pay gap audit have reported a wider gap this year.

Of the companies that had reported by mid-February (all companies with over 250 employees have to report by 4 April), the BBC found that the gender pay gap averaged out at 8.4 per cent, an improvement on last year which averaged out at 9.7 per cent.

However, of those companies, 74 per cent reported a pay gap which favours men, 14 per cent said they had a pay gap which favoured women and 12 per cent reported no pay gap at all.

According to the available data, the gender pay gap at energy giant Npower has grown from 13 per cent to 18 per cent since it last reported. The gap at car mechanics chain Kwik Fit grew from a negative gender pay gap - when women get paid more - of minus 15.2 per cent to a positive one of 14 per cent, while the gap at Virgin Atlantic widened from 28.4 per cent to 31 per cent.

One of the biggest gaps reported so far was RBS with an average gender pay gap of almost 37 per cent. As the analysis points out, a number of finance firms with 5,000 plus employees have large pay gaps, such as Lloyds, with a gap of just over 40 per cent.

In terms of sectors that have reported so far, construction has the highest pay gap, averaging out at just over 25 per cent, with finance and insurance coming a close second, followed by electricity and gas, communication and education.

London Heathrow Airport was among the firms that improved since they reported last year, posting a gender pay gap of 0.6 per cent compared with 6.5 per cent a year earlier.

The BBC analysis was based on the hourly median pay gap - that is the difference in pay between middle-ranking women and middle-ranking man – based on the data submitted by individual companies to the Government Equalities Office on 19 February. It referred solely to private sector firms which had provided gender pay gap data and had a consistent registration at Companies House for April 2017 and April 2018.

Emma Game of Thompsons Solicitors commented: “The difference in average pay between men and women’s pay is unacceptably high and the results published above are disappointing. There is currently no need for the employer to provide a narrative explaining how the gender pay gap is calculated and further pressure should be placed on employers requiring them to explain how they will close the gap going forward. The requirement to publish gender pay gap information does present an opportunity for unions and collective bargaining however, and trade unions are best placed to put the gender pay gap on the bargaining agenda by using the disclosure provisions under the TULR(C)A 1992”.

The BBC analysis in full can be found on their website.

The pay gap figures that have been submitted by companies to date are available on the government's website