The government has been described as sick and uncaring by an organisation representing more than 10,000 British nationals in Europe over NHS healthcare plans for pensioners in a no-deal Brexit scenario.

British nationals who have retired to EU countries have reacted with fury to what they describe as an insulting and offensive offer by the government to cover healthcare costs for up to one year if they had applied for or are undergoing treatment before exit day.

This is in contrast to the current reciprocal arrangement whereby the NHS reimburses EU member states for treatment of those who have paid into the UK national insurance system for a qualifying number of years.

“So if the person has paid into the system all their lives and retired to an EU country in good faith, with all the reciprocal arrangements in place, they could be left high and dry if they, say, get cancer after 29 March,” said Kate Husband, whose parents, both 80, a teacher and an architect, moved from Cornwall to join her and her husband in Brittany 25 years ago.

Pensioners will be eligible to return to the UK and get treatment on the NHS under the contingency plans, the health minister, Stephen Hammond, revealed in a statement on Tuesday.

“How can pensioners with cancer, cardiac problems or other major issues be expected to make or even afford repeated visits to the UK for regular vital treatment?” asked Dave Spokes, coordinator at Expat Citizens Rights in the EU (Ecreu), an organisation with 11,000 members across the EU.

“My wife was rushed to hospital in France the first week in February. She is still there six weeks later. How could we get her to the UK at a moment’s notice if she has a repeat problem?

“This is a sick, uncaring government. To cut citizens adrift through no fault of their own when they spent their entire working lives paying into the system, and when most had no say in the referendum, is despicable,” he said.

Husband said the notion of pensioners returning to the UK for healthcare was impractical as her parents, even if they wanted to, would not be able to sell up and return to the UK.

“I am right now standing beside a five-bedroom house with a beautiful garden which is on sale for about €90,000. That wouldn’t buy you a home in the UK,” she said.

Richard Fysh, who is retired in France, said: “People like myself who haven’t been to a doctor for nine years are being hung out to dry. My feelings are one of abandonment and anger.”

Fysh, a former teacher, is obliged to continue to pay taxes in the UK on his government pension. “Why should I be treated any different to a government servant in Yorkshire or Essex?” he said.

The government currently pays about £500m a year to cover costs for up to 180,000 pensioners settled in other EU member states, mostly in Spain, Ireland, France and Cyprus.

The arrangement saves the NHS about £450m a year because healthcare is cheaper in many EU countries. In 2017, a senior health department official told a parliamentary select committee that Spain charges an average of £2,300 for every pensioner it treats, compared with £4,500 charged by the NHS.

Hammond said on Tuesday the government was working closely with EU member states to protect the existing EU-wide system and welcomed action by individual states such as Spain which have taken steps to ensure the status quo in the event of no deal.

Sue Wilson, who runs the campaign group Bremain in Spain, said national insurance contributions were not a gift or a benefit but an insurance policy. “We’ve paid our dues so we expect to be covered,” she said.

Campaigners for Britons living in Italy said the government plans were shameful and could cost lives.

Delia Dumaresq, a committee member of British in Italy, said the year’s lifeline was “certainly a very small step forward” but predicted costly admin problems.

“How on earth is this ill-defined scheme to be understood by hard-pressed administrators in surgeries and hospitals in over 27 different countries? And if they do not know how to administer it, is there not a massive risk that they will either refuse treatment or insist the patient pays?” she said.