Backing the Republican Party's tax law could have been one of the worst votes of his career, retiring U.S. Sen. Bob Corker, R-Tenn., reportedly said after a Congressional Budget Office estimate released Tuesday showed the bill will add $1.9 trillion to deficits over a decade.

At the time Corker cast his vote, the Joint Committee on Taxation estimated the bill would cost about $1.1 trillion over a decade, the Hill reported.

But the CBO said the larger figure includes interest costs for servicing the debt and accounts for more recent economic data.

“If it ends up costing what has been laid out here, it could well be one of the worst votes I’ve made,” Corker said at a Senate Budget Committee hearing on the new CBO estimate, according to the Hill.

In early December, Corker voted against a version of the GOP tax-cut bill, making him the only Republican senator to do so, the report said.

At one point, he reportedly vowed to vote “no” for any tax bill that “added a cent” to the deficit. But he ultimately voted “yes” for the final bill.

After that vote Corker blasted critics who asserted he backed the plan only after the addition of a last-minute provision that stood to benefit him personally. The provision allows owners of large commercial real estate holdings -- such as Corker -- to deduct a percentage of their “pass through” income from their taxes.

The Tennessee Republican also criticized the omnibus funding bill Congress passed in March, Business Insider reported.

“None of us have covered ourselves in glory. This Congress and this administration likely will go down as one of the most fiscally irresponsible administrations and congresses that we’ve had,” Corker said.

The new CBO estimate also showed the U.S. will reach an annual budget deficit of more than $1 trillion beginning 2019, Business Insider reported.