Monitor’s capacity to regulate foundation trusts in difficulty may come under “unsustainable pressure” due to the growth in risk across the sector, the National Audit Office has found.

However, in a report published today the NAO also said the regulator had achieved value for money and been effective in helping underperforming foundation trusts to improve.

The NAO said that while it was difficult to assess Monitor’s impact on foundation trusts, staff at case study trusts said they took “faster or more effective action, or both, because of Monitor’s interventions than they would otherwise have done”.

The NAO said Monitor, which has a core budget of £48m in 2013-14, was most effective when a trust was in difficulty because of internal issues, such as poor leadership or financial management.

However, it said its influence was more limited where “a trust’s problems are down to underlying issues in the local health economy, such as where commissioners are also in financial difficulty”.

The NAO said Monitor had “changed its approach” to these trusts recently by working with local and national stakeholders to find solutions for challenged health economies, and it urged Monitor to continue using its “informal powers of influence and persuasion to broker solutions” in this way.

The auditor also said Monitor had to do more to explain how it would balance its responsibilities to prevent anti-competitive behaviour while enabling integrated care.

Margaret Hodge, chair of the Commons public accounts committee, said she was “reassured” by the NAO’s findings.

She added however that the regulator had to “adapt… to remain fit for purpose” to deal with the present economic climate and additional responsibilities, and that it was important its latest recruitment campaign “quickly recruits the 113 posts that are currently vacant”.

Increased risk in the foundation trust sector – where a quarter of trusts are currently in deficit and 25 are in breach of their licence – has created a bigger workload for Monitor, as HSJ has recently reported.

At the end of last year Monitor employed 337 staff, but in January it announced it would be adding an additional 86 posts to its regulatory workforce alone.

Monitor chair Baroness Hanham said: “We are continuing to work to ensure that the NHS provides the quality services that matter to patients.”