Half of all MPs’ staff are suffering from clinical levels of psychological distress, according to a groundbreaking study that will hasten calls for culture change in Westminster.

Parliamentary aides said they were at “breaking point” after years of crises, from Brexit to Covid, a lack of support from superiors and abuse from the public.

The survey of nearly 200 members of MPs’ staff, the first of its kind in the UK, found that 49.5% met the medical threshold for psychological distress – more than twice the level in the general population.

Nearly three-quarters of MPs’ caseworkers felt “emotionally isolated” and more than a third had experienced abuse, bullying or physical aggression, the study found.

The wellness working group, a cross-party group of MPs’ staff, described the findings as “shocking” and called for urgent “cultural change from the top”. It said: “This report highlights what many staff already know from personal experience, although the true scale of the problems identified is very concerning.”

The findings will raise further concerns about the working culture in Westminster, ahead of the publication of the Sue Gray report on Partygate. The report is expected to criticise the leadership of senior figures in Downing Street over social gatherings held in breach of Covid restrictions.

Dr Ashley Weinberg, an occupational psychologist who carried out the study, said the 49.5% of MPs’ staff suffering from distress was “far higher” than in comparable jobs. It is twice the level experienced by the population at large, according to the study, and higher than the 40% of MPs deemed to be under similar strain during the 2009 expenses scandal.

Weinberg measured aides’ anxiety using a screening tool called the General Health Questionnaire-12, which is widely used to measure psychological distress. Almost three-quarters of MPs’ aides said the job was “emotionally draining”, while one in five described it as “harrowing”. Nearly half said parliament could do more to support them in their roles.

Parliamentary aides likened their roles to an “unofficial emergency service” as they field an “unrelenting tide” of often-desperate calls and emails from members of the public. They felt under-resourced and ill-equipped to deal with the growing workload.

Weinberg found a “palpable” concern among staff over their safety, with almost one-fifth of workers saying they felt in danger for themselves or colleagues. One said: ‘The office is unsafe. It has no windows and we are frequently approached by aggressive members of the public when in the office.”

About a dozen staff had experienced bullying or harassment, the report found, with one aide saying: “I enjoy working with colleagues as a result of solidarity from the bullying many in the team face from the MP.”

Thomas Fairweather, an executive member of the working group, said staff feared the pressures would intensify as the cost-of-living crisis was felt more keenly by constituents.

He said: “Staff are too used to the horrible, sickening feeling that coming down the line there will be another huge influx of people in desperate situations, needing help in ways that teams are not trained for. With more suitable training, resources and changes to fix the wellbeing problem, we could do so much more.”

The report recommends the introduction of greater support for MPs’ staff, including mandatory training for coping with suicidal constituents. It also endorses the launch of a mediation service to address grievances.

Staff who work for MPs are employed directly by the MPs, rather than by any one political party or the House of Commons. This adds to the anxiety, aides say, because it becomes more difficult to raise concerns about workload or bullying.

A House of Commons spokesperson said: “Staff who work in MPs’ offices perform a vital role supporting constituents in some very difficult circumstances. The support and guidance for MPs’ staff have vastly increased over the past years based on feedback, including setting up a members services team dedicated to working with them wherever they are based.

“However, we are always looking at ways we can improve that support, including recently announcing a Speaker’s conference on employment status of MPs’ staff, and the ideas in this report will feed into how we do that.”