HARRISBURG — Lou Barletta, the former congressman seeking the Republican nomination for governor of Pennsylvania, has signed a pledge from a conservative anti-tax Washington-based group that commits him to oppose tax increases.

The pledge, sponsored by Americans for Tax Reform, commits the signer to the state’s taxpayers to “oppose and veto any and all efforts to increase taxes.”

Barletta, of Hazleton in northeastern Pennsylvania, said on Twitter on Friday that he was proud to sign it.

Pennsylvania “is not a business-friendly state” and taxes its employers more than any other state, except New Jersey, Barletta said.

As governor, Barletta said, he will lower taxes.

Americans for Tax Reform lists just 13 of 27 sitting Republican governors who have signed it. It lists no Democrats.

The last Republican governor of Pennsylvania, Tom Corbett, also signed the pledge. Corbett, then the state attorney general, did so in February 2010 when he was running in a contested primary against a conservative state lawmaker.

Corbett’s pledge became a defining issue for him and a constant presence in the Legislature’s debates in fiscal and policy matters.

Despite his general reluctance to increase the financial burden on taxpayers, Corbett ultimately signed legislation raising taxes on motor fuels and scores of fees on items including birth certificates, court filings and hauling permits. Corbett also signed a major oil and gas drilling law in 2012 that allowed counties to impose an “impact fee” on new Marcellus Shale wells.

During his unsuccessful campaign for a second term in 2014, Corbett said he believed he had fulfilled the spirit of the pledge.

Asked whether he regretted making the pledge, he said he couldn’t have foreseen the demands on the state for new revenue.

“Nobody has the crystal ball that’s going to say, ‘Well, I can say this and not worry about it; I can say that and not worry about it,’” Corbett told The Associated Press at the time.

Barletta is running in a crowded field for the GOP nomination in next May’s primary election and, on Monday, the field grew with the entry of Guy Ciarrocchi, who just stepped down as president and CEO of the Chester County Chamber of Business and Industry.

Gov. Tom Wolf, the Democrat who beat Corbett, is constitutionally barred from serving a third term.