He said increasing electricity prices was a "difficult decision" and that Centrica had held off on doing so for many months longer than most suppliers in order to protect customers.
"Centrica delivered a solid first half financial performance despite reduced energy demand due to warm weather and strong competitive pressures, and we remain on track to achieve the 2017 targets we set out in February", said group chief executive Ian Conn.
"British Gas customers should take matters into their hands and switch today to a fixed rate tariff with a "Big Six" or other reputable supplier".
He said: "This is British Gas' catch-up price hike".
Centrica shares were up 2.9% on Tuesday morning at 204.10 pence.
Co-founder Will Hodson said: "British Gas announcing a price rise as they make half a billion in profit is the ultimate slap in the face for families".
Centrica's release on Tuesday gave a bit more detail of the reason for the rise in electricity prices, saying: "The price rise reflects increasing delivery and environmental and social policy costs since 2014, and also the growing additional costs related to the United Kingdom smart meter rollout".
The increase comes soon after Centrica posted half-year results revealing that earnings from its consumer business plunged by more than a quarter after it lost 377,000 United Kingdom customer accounts in the first half.
We have announced today that because we are anxious about vulnerable customers this winter that an additional 200,000 customers who get a wrap home discount will be protected from the price rise.
But critics of the move, including the government itself, hit back at the assertion the price rise was largely driven by policy costs.
As you can see, the best dual fuel tariff deal costs £834 a year, £210 less than what British Gas is charging customers on its standard tariff right now and £286 less compared to the cost from 15 September. And that means if, as is possible, we see another batch of rises this coming winter, its customers will feel like they've been price-slapped twice in rapid succession.
During the election, the Conservatives announced plans to introduce a cap on so-called default energy tariffs, after attacking the industry for offering "poor value" and failing to treat customers in a "fair and reasonable" way.
Researcher for the Common Weal Scottish think tank, Craig Dalzell, said that the hike had once again highlighted the "oligopoly" in the UK's energy market. British Gas claim the rise is because of increased costs but Ofgem data shows that all their costs - wholesale, network and policy - have dropped by nine per cent since December 2016.