They are divided over the Treasure Bill, designed to reform medieval law covering the discovery of lost gold and silver - which will receive its second reading next week - and a code calling for detectorists to report any antiquities which might have historical interest.
David Graham, honorary secretary of Surrey Archaeological Society, and an adviser on the Bill, has been among those pushing for change, alongside historians and institutions including the British Museum.
Their concern was heightened a decade ago, when a Roman temple at Wanborough, near Guildford, in Surrey, was plundered by unscrupulous metal detectorists, known as "nighthawkers". An estimated pounds 1.5m worth of Iron Age and Roman coins disappeared.
There are at present 30,000 metal detectorists in Britain, who are estimated to find around 400,000 items a year, although only a minority of these are either precious or of significant historical interest.
The Bill extends the definition of treasure to cover anything that has a 5 per cent precious metal content, compared to the existing 50 per cent. Other objects which do not contain precious metal are also covered, if found as part of a hoard, and no object needs to have been buried with the intention of being recovered, to be protected by the law.Reuse content