Nearly half of British troops regularly consider quitting the army and navy because of plummeting morale, poor equipment and low pay, a Ministry of Defence survey of more than 24,000 military personnel has found.

Some 47% of soldiers and army officers periodically considered handing in their resignation. The proportion was the same among Royal Navy personnel, while the figure was 44% in the RAF.

It is the first study of its kind to gauge joint attitudes across the army, navy and RAF and reveals alarming levels of stress and unhappiness among service personnel. The research is likely to call into question Britain's ability to sustain campaigns in Afghanistan and Iraq.

Many of those questioned highlighted the pressures of fighting on two fronts, while 45% said they were not happy with the level of separation from friends and family. Some 38% said the short gaps between tours of duty made them more likely to leave the forces.

In the army, nearly three-fifths of those questioned rated the level of morale as "low" or "very low", although individuals said their personal morale level was high. In the RAF, three-quarters thought morale was low, compared with 64% in the Royal Navy and 38% in the Royal Marines.

The survey was carried out between July and October last year - a time when more than 30 personnel died in the two main combat zones. But since then the casualty rate has remained high, particularly in Afghanistan.

Patrick Mercer, the Tory MP for Newark and a former commanding officer, said the findings reflected the strains on military personnel. "I think the tempo of operations has produced such a level of stress on the families that it is no wonder so many are thinking of leaving."

The armed forces minister Derek Twigg said: "Since the survey was conducted we have already implemented a number of important changes, such as the recent pay rise, an adjustment to the operational bonus and the introduction of childcare vouchers. Over the next 10 years, we are also spending £8.4bn on accommodation, an area that is a high priority."

He said the government was planning to bring forward more measures to improve conditions later this month, and there was "always more that can be done".

In the past, regular Continuous Attitude Surveys have been carried out separately for each of the services.

Last November the head of the British Army expressed concerns about poor morale and raised the issue of the strain on resources from operations in Iraq and Afghanistan. General Sir Richard Dannatt said soldiers felt "devalued, angry and suffering from Iraq fatigue", and catalogued disquiet on a wide range of issues facing soldiers, including poor housing.