The owner of Boots has denied overcharging the NHS for a mouthwash used by cancer patients.
The Times alleged on Saturday that Walgreens Boots Alliance charged £3,220 for the pain-relieving product that can cost £93.
Health Minister Steve Brine called for a possible investigation by the Competition and Markets Authority (CMA), which confirmed it was considering a complaint.
A Walgreens Boots Alliance spokesman said: “We firmly reject accusations of overcharging the NHS.
“Our senior company leaders have already recently met with officials from the Department of Health to discuss the specials products.”
Mr Brine said the public would take an “extremely dim view” of any company found to be “exploiting” the NHS.
“We have asked the Competition and Markets Authority to consider investigating as a priority,” he added.
“We have changed the law to enable us to place pharmacies and manufacturers under much stronger scrutiny.
“Where there is evidence of collusion between pharmacies and suppliers swift action will be taken to claw back funds and penalise offenders”.
The newspaper’s investigation said the mouthwash, a “special” used to treat patients with sores caused by chemotherapy, was bought at least five times from Boots’ parent company at a cost of between £1,843 and £3,220 between May 2013 and last year.
Specials are unlicensed medicines prescribed when there is no licensed alternative.
A CMA spokeswoman said: “We can confirm we have received a complaint and are considering it.”
An NHS England spokesman said: “All pharmacies should seek to secure best value in preparing ‘specials’ for patients.”