More than one in three separated parents believe the UK’s “pitiful” paternity leave played a part in their breakup, research has suggested.

The campaign groups, The Dad Shift and Movember, said hundreds of thousands of families were falling apart as a result of a parental leave system described by MPs as “one of the worst in the developed world”.

A survey commissioned by the groups found that 69% of single parents said the UK’s two-week, low-pay paternity leave made it harder to share parental responsibility, exacerbating gender inequalities.

Labour MPs will this week urge ministers to speed up reforms to the system following an 18-month government review. Changes are not due to be set out until next year.

Introduced in 2003, statutory paternity leave allows most new fathers and second parents in the UK to take up to two weeks off work. Those eligible receive £187.18 a week or 90% of their average earnings, whichever is lower.

However, this amounts to less than half of the minimum wage for someone over 21 and disqualifies those who are self-employed.

The cross-party Commons women and equalities committee said last year the UK’s “broken” two-week paternity leave was “one of the worst in the developed world” and was entrenching a stark gender disparity with significant economic and social costs.

In Spain, new fathers can take 16 weeks off work at full pay and in France working fathers can spend 28 days at home while being paid. Families in Sweden are entitled to 480 days of paid parental leave, with 90 days reserved for fathers.

Maya Ellis, a Labour MP who on Friday will lead a Commons debate on the topic, said the UK’s two-week offer meant that parental equality was “out of reach” for all but the wealthiest.

“Working families in constituencies like mine are breaking apart under the strain,” said the MP for Ribble Valley in Lancashire.

The Labour peer Frances O’Grady, the former Trades Union Congress general secretary, told the Lords that the need to reform the UK’s “pitiful” system was urgent.

A survey of 553 separated parents by the polling firm Whitestone Insight, due to be published on Thursday, found that the UK’s two-week paternity leave made it more difficult to share childcare load.

Thirty-nine per cent said not sharing caring responsibilities contributed to the breakdown of their relationship.

Research published by the government suggests that equal parenting reduces separation risks by up to 92% compared with when mothers are largely responsible.

Official figures suggest that as many as two in five new fathers do not take up paternity leave, with most saying they cannot afford to take the time off work.

Alistair Strathern, a Labour MP, said: “Two weeks might work for a trip to Spain, but as far as the time needed to support your partner, bond with your baby and step up into being an active dad – it’s just nowhere near enough.”

A study from Iceland found that the introduction of three months’ paid paternity leave in 2000 led to a “considerable” reduction in divorce rates.

The Commons women and equalities committee, chaired by the Labour MP Sarah Owen, has urged ministers to increase the two-week offer to six weeks and include self-employed workers.

It said the cost of the reforms would be substantial – statutory paternity pay cost the government £77m in the year to March 2025 – but that this would be “far outweighed by the wider societal and economic benefits,” adding: “Tinkering around the edges of a broken system will let down working parents.”