The UK has slipped out of the top 20 countries for gender equality and the gap between men and women in the workplace has widened, according to a report that places Britain behind the Scandinavian countries and the Philippines.

Research by the World Economic Forum (WEF) – the body behind the high-powered annual Davos summit – found the UK has slipped from 18th to 26th in the rankings of its Global Gender Gap Report, part of a steady decline from the forum’s inaugural league table in 2006, when the UK was ranked ninth. The UK also recorded its lowest overall score since 2008.

As in 2012 and 2013, the list was dominated by northern Europe and the top four countries remained unchanged, with Iceland first, Finland second, Norway third and Sweden fourth. However, the index, which measures equality gaps in countries rather than overall levels, also rated a number of middle-income and developing countries above the UK, including Nicaragua (sixth), Rwanda (seventh) and the Philippines (ninth).

While the UK failed to make the top 20 in any of the report’s four categories – economy, education, health and politics – the drop in its overall rating this year was chiefly attributable to a significantly lower score in “economic participation”, which measures attributes such as the ratios of women in the workforce, wage equality for similar work done by men, and the number of women in senior roles.

The WEF added: “[In the economic participation subsets the UK] appears to remain some way off, with the country ranking 48th in terms of both labour force participation and wage equality and 66th for estimated earned income.

“Unlike many of its peers, it has still yet to close its educational attainment and health and survival gaps (ranking 32 and 94 respectively), while it does moderately better in the fourth area we measure, political empowerment, where it ranks 33rd.”

Critics of the varied campaigns for gender equality can point to the UK’s faster economic recovery when compared with most other developed economies. However, Ann Francke, the chief executive of the trade body the Chartered Management Institute, said a UK economy where women benefited less than men was “unsustainable”.

Francke, whose organisation also produces annual research on the UK’s gender pay gap, added: “The issue in the UK is that while there are more women in the workplace they tend to be in the lower-level positions. The pay gaps continue to be alarmingly large for men and women doing the same senior role.” Meanwhile, other observers said the UK could be slipping down the list because of the way in which it structures childcare and paternity leave.

Spencer Thompson, senior economic analyst at the IPPR thinktank, said: “France and UK spend more on childcare – but tend to do it through cash transfers to parents. In countries like Sweden, Iceland and Norway they provide more services … either free at the point of use or very heavily subsidised. In UK we have really high childcare prices as we are injecting lots of cash into the system.”

Saadia Zahidi, lead author of the WEF report, said: “Much of the progress on gender equality over the last 10 years has come from more women entering politics and the workforce. While more women and more men have joined the workforce over the last decade, more women than men entered the labour force in 49 countries.”

The WEF report is the latest in a line of studies and campaigns seeking to highlight gender inequality issues. Last week a global study of almost 6,000 MBA graduates by research group Catalyst found that the most highly qualified female business graduates lack the ambition of male counterparts in sectors such as engineering, manufacturing and natural resources.

That finding appeared to be supported by comments from Moya Greene, chief executive of Royal Mail and one of only five female chief executives in the FTSE 100.

In a speech last week, she said: “It’s still disappointing when you see how young women view their ambition – and how others view that ambition. To be a CEO it’s really hard work and you really have to want to do it. For women, even in 2014, that can be a problem.”

In 2011 the UK government launched a review of women on boards by Lord Davies, which set a target of having a minimum of 25% female representation on FTSE 100 boards by 2015. The percentage of female FTSE 100 directors has since risen from 12.5% to 22.8%, although the latest figures show that 61 members of the FTSE 100 have yet to reach 25%. The laggards include some of the index’s largest firms, such as Reckitt Benckiser, the household products group behind brands such as Dettol and Vanish, the oil giant BP and the commodity trading firm Glencore.

Ruth Sealy, a lecturer and researcher in organisational psychology at City University London, said: “One of the approaches beginning to have an effect is this continual push for transparency in reporting. It is beginning to have an impact as it makes organisations a lot more aware about what’s going on internally and a bit more embarrassed about it. We are not in the same place we were five years ago. The whole women on boards thing has had an impact. It is finally beginning to have an impact on chief executives.”