The government has ruled out any immediate extra money to help tackle cable theft on the railways.
The Transport Select Committee had said "as a matter of urgency" more funds should be given to the metal theft task force beyond the current £5m.
Chairman Louise Ellman said she was "disappointed" and ministers "should not sit back and wait" while theft continued to cause huge disruption.
Ministers said they would keep the issue of funding "under review".
The British Transport Police (BTP) metal theft task force is attempting to increase prosecutions and disrupt organised criminal gangs.
It is also carrying out spot checks on scrap metal dealers, a key conduit for stolen material.
The government said more than 100 officers countrywide were part of the task force, and further details of their plans would be announced shortly.
"Given the progress it is making with legislative measures to tackle metal theft... the government does not consider at this stage that further funding is likely to be required to extend the scope or or duration of the metal theft task force, but will keep the issue under review," it said.
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The government's announcement must be translated into action if this unacceptable situation is to be addressed
Louise Ellman Transport Select Committee chairwoman
The transport committee made a number of other recommendations, among them the creation of a new criminal offence of aggravated trespass on the railway.
However, the Department for Transport (DfT) said it wanted to "consider further" whether there was evidence to justify such a move, given "the steps already in hand to increase the resources available in the short term for enforcement".
It said it had tabled amendments to the Legal Aid, Sentencing and Punishment of Offenders Bill - currently awaiting Royal Assent - which satisfied other recommendations made by the committee.
These will prohibit most cash payments for scrap metal, require records to be kept of anyone selling scrap, and increase the maximum fine available for wrongdoing.
"This [will] provide a direct means of tracking the financial audit trail for sales of scrap metal, and hence go a substantial way towards enabling the identification of the sellers of stolen material," the DfT said.
The forthcoming bill will also extend police powers to search both registered and unregistered scrap metal dealers, the department added.
Labour MP Mrs Ellman said: "I am disappointed that the government will not provide further resources for the police to tackle metal theft despite BTP's leading work in this area.
"Cable theft cost Network Rail £16m last year and disrupted [millions of] journeys, so the government should not sit back and wait whilst these figures are repeated.
"The government's announcement must be translated into action if this unacceptable situation is to be addressed with the urgency that is required."
The ban on selling scrap for cash excludes itinerant, house-to-house metal collectors, who will be allowed to continue if they are registered with their local authority.
Labour MP Graham Jones has voiced concerns about the potential loophole, arguing that many itinerant collectors had been "operating illegally" for many years and were "often the point at which stolen metal infects the supply chain".
He urged police and councils to take advantage of new powers to prosecute and fine any who failed to comply with registrations.