The implementation of the government's flagship vascular screening programme for 40 to 74-year-olds must be clearly set out and carefully managed, primary care specialists have warned.

Health secretary Alan Johnson announced on Tuesday that the proposal to offer vascular checks via GP practices, community health facilities and pharmacies would be rolled out next April, following consultation on implementation.

The Department of Health hopes the programme, costed at£250m a year for checks and subsequent care, will reduce inequalities by targeting unregistered patients as well as those on GPs' lists.

Neither Mr Johnson, nor associate chief medical officer Bill Kirkup, would reveal the value of potential savings, saying only that the plan, announced by prime minister Gordon Brown in January, met NICE clinical and cost-effectiveness thresholds.

But senior lecturer in public medicine at Birmingham University Tom Marshall said it had a "broad brush" approach and could lead to duplication where GP-registered patients were receiving advice from pharmacies.

He said: "It's one thing to get people in [for] a check-up, but unless you've got a clear care pathway and clear systems and protocols set up, it doesn't work terribly well."

PCT Network director David Stout said the focus on prevention seemed "sound" but it would be important to avoid duplication. "That's where the implementation plan is crucial - it is a potential risk," he said.

And chairman of the BMA's GPs committee Dr Laurence Buckman warned large-sale screening would affect access.