One in five cohabiting mums (22%) said their relationship with their partner got worse during the coronavirus lockdown, according to a major new study.
Overall, one in five couples said their relationship had improved during lockdown as they were forced to spend more time together, but the study of 2,559 parents revealed significant variations, with cohabiting mothers faring worse in almost every category.
They were three times as likely as other respondents to report a worse relationship, and four times as likely to say that they and their partner got on each other's nerves "most" or "all" of the time.
They were five times as likely to say that they quarrelled "most" or "all" the time with their partner, and had double the odds of regretting living together.
When it came to household chores, they were less likely than married mothers to say that these were divided fairly, while one in 10 cohabiting mums said they had or were considering splitting up from their partner.
Married, self-employed parents fared the best, with three in 10 (29%) reporting a better relationship.
The report reads: "Our baseline hypothesis was that those with higher initial levels of dedication in their relationship would view the additional constraint of lockdown positively whereas those with lower initial levels of dedication would view it negatively.
"We also expected a gender effect whereby a lower level of dedication among cohabiting men would lead to less satisfied cohabiting women. Our results strongly support this view."
It continues: "[T]he average married parent entered lockdown with relatively high levels of dedication. Most thrived as a result. For them, enforced time together at home has been (mostly) a pleasure.
"However, for the average cohabiting parent, overall levels of commitment are less explicit and levels of ambiguity are typically higher.
"If some proportion of cohabiting mothers are more dedicated to the relationship and some proportion of the cohabiting fathers less dedicated, then it will be the cohabiting mothers who feel the weight of the additional constraint most negatively.
"For them, lockdown has taken a relationship with a degree of ambiguity and uncertainty that is manageable under normal circumstances and forced them to spend extra time with somebody who they suspected may not be as committed.
"In short, lockdown shines a spotlight on relationships where one partner is either explicitly or secretly less committed."
Sir Paul Coleridge, founder of the Marriage Foundation said the Government must redouble its efforts to promote stable, committed relationships.
"Once again research would seem to show clearly that serious, forward-looking, formal commitment i.e. marriage, adds a crucial ingredient to long term relationships which is very often absent with mere informal cohabitation," he said.
"So, when these informal relationships are stress tested by outside events, as they have been by Covid and lockdown, they are more liable to buckle under the added strain.
"Why is that? The answer is surely that ambiguity is the very antithesis of long-term stability and security, two vital objectives for all satisfying, loving relationships."