OAKVILLE, Ont. -- Britain's competition regulator is accusing Canadian specialty drug company Concordia International Corp. of overcharging for a thyroid drug after raising the price by nearly 6,000 per cent between 2007 and 2017.

In a statement of objections, the Competition and Markets Authority is alleging Concordia abused its market dominance in the supply of liothyronine tablets.

It says that the price per pack rose from about 4.46 pounds in 2007 to 258.19 pounds (C$437) in July 2017.

Concordia (TSX:CXR) says it does not believe that competition law has been infringed.

The company, based in Oakville, Ont., says the pricing of liothyronine has been conducted openly and transparently with the Department of Health in the United Kingdom.

Liothyronine tablets are primarily used to treat hypothyroidism, a condition caused by a deficiency of thyroid hormone.

The CMA says although liothyronine is not the primary treatment for hypothyroidism, for many patients there is no suitable alternative and, until earlier this year, Concordia was the only supplier.