U.S. Rep. Joaquin Castro, D-San Antonio, directly accused Gov. Greg Abbott Wednesday of engaging in possibly illegal “pay to play” politics by promising to help a major donor move legislation pushed by insurance companies.

In a letter addressed to the governor and written on congressional letterhead, Castro referred to a May 20 email exchange between Abbott’s office and Richard Weekley, CEO of Texans for Lawsuit Reform.

Weekley had asked Abbott to “personally intervene” to help pass the bill, saying that Democrats — and their major donor Steve Mostyn — stood to benefit by killing it.

Castro said the email exchange “speaks to the shadiness and corruption that has characterized state government for several years, including the issuance of hundreds of millions in no-bid contracts to cronies that occurred” when Abbott was attorney general.

Texans for Lawsuit Reform (TLR) and Weekley have given Abbott at least $720,000 since 2001, records from the Texas Ethics Commission show.

“You exhibit an eagerness to take official action to please a donor for the purposes of political retribution,” Castro wrote. “For years, members of the Texas business community and others have spoken of state leaders’ tendencies toward ‘pay to play’ and official retribution for supporting persons politically opposed or out of favor with state officeholders.”

He said the email exchange “confirms that reality,” and calls Abbott’s actions “unethical and quite possibly illegal.”

Abbott spokesman Matt Hirsch did not return messages left via phone, text and email Wednesday afternoon.

In the May 20 email, Weekley wrote to Abbott that the pro-insurer bill was “good policy and good politics.”

“Having Mostyn rape the insurance companies of hundreds of millions of dollars will harm consumers across the state as well as hurt the politicians who Mostyn will try to defeat,” Weekley wrote.

In a postscript he added, “We can’t let the House, composed of 98 Republicans and 52 Democrats, have a legislative victory for Mostyn, who gave over $25,000,000 to Democrats over the last five years.”

A few hours later, the governor’s office responded via email: “We are working it. Spoke with the Speaker about it earlier today.”

Weekley addressed the email directly to the governor, and the documents were provided to The Texas Tribune in response to a request for copies of emails sent by Abbott himself.

However, the governor’s office has refused to say if it was Abbott or someone else who authored the email.

At issue was Senate Bill 1628, which would have erected hurdles for homeowners and businesses that wanted to sue insurance companies that don't deal with them fairly, or don't adequately pay out on claims made under property and casualty insurance policies, such as losses after a storm, fire or accident.

The legislation ended up dying in committee in the final days of the recently concluded session after a wide swath of business interests — from oil and gas companies to auto dealers — said it would weaken their insurance policies and put them at a disadvantage in disputes over property damage claims.

Disclosure: Steve Mostyn is a major donor to The Texas Tribune. A complete list of Tribune donors and sponsors can be viewed here.