Scottish Power has become the second of the Big Six energy suppliers to hit out at Conservative plans to introduce price caps on household bills.
The Conservative Party is expected to include proposals for a cap on expensive standard variable energy tariffs – the most common rate paid by households – in its forthcoming manifesto.
But Keith Anderson, chief corporate officer of Scottish Power, told the BBC Today programme such a cap on prices could "stop competition" and "actually damage customers in the long run".
He added: "Price controls tend to lead to less competition, and therefore less benefit for customers."
Scottish Power, which serves around five million customers, said it was better to move households away from standard tariffs onto more competitive charges.
The market had been expecting a clampdown on these rates after most of the Big Six firms – Scottish Power, SSE, British Gas, EDF, Npower and E.ON – announced price hikes earlier this year, sparking outrage from MPs and consumer groups.
These groups complained that consumer prices for gas and electricity lifted, despite wholesale prices remaining lower than they were in 2014.
Scottish Power's comments echo similar objections by Iain Conn, the chief executive of British Gas-owner Centrica, who said on Sunday that price regulation "will result in reduced competition and choice, stifle innovation and potentially impact customer service".
British households have spent £7bn more than they should have on energy bills over the last three years, small energy supplier First Utility said last month.
The idea of a cap on household energy tariffs was first put forward by former Labour leader Ed Miliband in the run up to the 2015 general election.