Dozens of United Kingdom businesses still need to submit their gender pay figures ahead of Wednesday's midnight deadline.
She added: "Flexible working is still not as widely available as it needs to be, together with pay structures which do not disadvantage part time workers - women or men".
However, many employers have revealed the difference in their companies is greater than this. Amazon's topline data includes the thousands of staff who work in its warehouses across the UK. According to BT's main public company listing, women are paid 2.3% more in terms of median hourly rate.
The managed hosting provider has a baseline mean gender pay gap of 0 per cent.
Yorkshire Water and its sister company Loop Customer Management released their gender pay gap figures yesterday (3 April) for 3,500 employees. The hourly median gap was 24%, with men being paid more.
In another - Abellio Scotrail - the difference in median hourly pay is 27.2 per cent.
The news has come to light due to a change in United Kingdom law which stipulates that any company in the market with more than 250 employees must reveal their gender pay gap stats by April 5 (tomorrow).
Many well-known names have reported large gender gaps, with Ryanair a notable example. "We have programmes that we're continually working to further improve, to actively recruit and help advance more women into senior and technology-focused roles as we grow our business here in the United Kingdom".
The Sun's parent company News UK revealed it had an overall pay gap of 15.2 per cent across all its subsidiaries last week. However, as with Amazon, the figures appear to be skewed by the fact the company employs a significant number of men in low paid roles outside of its corporate offices.
The charity also claims that this exercise has the potential to be a game changer in prompting people to talk about pay and find out what their colleagues earn -and it is calling on women everywhere today to do just that. This results in women earning on average £1.13 for every £1 men earn. "The increased transparency that gender pay reporting has brought has further fuelled the debate about how we're supporting different groups in society towards fulfilling, fair, and rewarding opportunities and work for all". She welcomed Virgin Money setting a target to achieve a 50:50 gender balance throughout the firm within two years.
And 6,493 companies pay men more than women, in comparison to 1,213 that pay women more than men.
Of the carrier's 554 pilots, more than 540 are men; meanwhile its lower paid cabin crew are predominantly female.
Kate Andrews, news editor at the Institute of Economic Affairs, a UK-based free market think tank, strongly opposes the reporting measures, calling them "worse-than-useless".
The publisher has also said it will ensure a diversity in candidates for all Senior Leadership Team roles.
The UK is one of the first countries in the world to require companies to submit the data.
All figures are a mean average. A near-equal proportion of women (75.3%) and men (74.3%) received a bonus.
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