The Science and Technology Facilities Council has admitted to concerns that long-term damage could be done to UK nuclear physics by the cuts that it has imposed on the subject's funding.
The admission comes in the council's operational plan for 2011-12, which was published last week.
Total funding for nuclear physics will be ?5.8 million, compared with around ?9 million prior to the 2007 Comprehensive Spending Review.
The council says this "significant" reduction was not a policy decision but the result of the prioritisation exercise it carried out in 2009, in which "a number of nuclear physics projects did not fare well".
"Funding for the nuclear physics grants round now under way is...very constrained over the next few years, and it is not clear at what level existing support in some key areas can be maintained," the plan admits.
It also expresses fears that the "lack of a development line for future nuclear physics projects" could do long-term damage to the subject, and commits the STFC to exploring the "scope for opening up some modest level of support for future planning".
But a spokeswoman for the council confirmed that any extra funding for new projects would have to be offset against reductions in spending on existing projects.
Martin Freer, professor of nuclear physics at the University of Birmingham, said the budget fall had led to the erosion of the UK's leadership in the field.
"The subject is under severe pressure within the budgets set by the STFC," he said. "There are groups within the UK who now have had sustained periods without any real funding for research and key people are leaving the UK."
He said the council had not previously consulted on how to safeguard the subject's future, but added that academics would "welcome such discussions".
Sean Freeman, professor of nuclear physics at the University of Manchester, also welcomed the STFC's offer, but said many felt it was "too little and too late" to prevent damage.
He added that there was a feeling that "the process used in the prioritisation exercise did not treat nuclear physics very well" and that funding for nuclear physics was already low by international standards.
The operational plan also announces that the STFC's workforce will be reduced by 10 per cent by the end of 2011-12, with a "greater reduction" in senior staff.
The spokeswoman said that the council would shed scientific and administrative staff as a result of changes to its programmes and reductions in its administrative budget.
In astronomy, the council will press on with its controversial policy of withdrawing some UK-led ground-based optical and infrared telescopes. But Robert Massey, deputy executive secretary of the Royal Astronomical Society, welcomed its pledge to "work to ensure that options for continued access to key capabilities are fully explored".
"This would take a relatively small amount of money but would go a long way towards offsetting real damage to the astronomy research base," Dr Massey said.
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