A government-backed review has found that FTSE 100 companies are on track to meet its target of having a third of their board positions held by women by 2020.
However, that is conditional on businesses continuing the progress made over the last three years, with almost 28% of board roles in the UK's biggest firms now occupied by women.
This is more than double the 12.5% that were in 2011, while the number of all-male boards in FTSE 350 companies has fallen from 152 to just eight since then.
Business minister, Margot James, said: "We have seen time and time again that our most successful companies are those that champion greater diversity and inclusion.
"Businesses have made great strides in recent years to increase senior female representation in order to reap both the societal and economic benefits."
All FTSE 100 companies, and 96% of FTSE 250 companies excluding investment trusts, voluntarily responded to the 2017 Hampton-Alexander Review's requests for their gender diversity data.
However despite the progress that has been made, review chair, Sir Philip Hampton today called on FTSE 350 companies to quicken the pace of change on boards.
He has extended the 33% target for female representation to senior leadership positions of all FTSE 350 companies, with the voluntary goal previously only applying to FTSE 100 firms.
However, Hampton said that at least 40% of appointments to senior positions would have to be filled by women over the next three years if FTSE 350 firms are to hit the ambitious targets.
"This year we have seen progress pick up on FTSE 100 boards and go slow elsewhere," he continued.
"We must now renew commitment to this important issue for UK business to fully harness the under-utilised potential of the many talented women in the workplace.
"We should be seeing all FTSE companies now making strides to improve the gender balance at the top."
