Rand Paul lashed out at his Republican colleagues for aiming to keep too much of Obamacare in a Senate bill expected to be voted on next week.

Paul wrote in an op-ed in Brietbart News that Republicans campaigned on repealing the entirety of the law, but aren't living up to those promises. His piece came a day after Senate GOP leadership announced it planned to keep some of Obamacare's taxes on investments and Medicare to fund its beleaguered bill, which Paul has opposed.

"Now too many Republicans are falling over themselves to stuff hundreds of billions of taxpayers' dollars into a bill that doesn't repeal Obamacare and feeds Big Insurance a huge bailout," the Kentucky Republican senator wrote. "Obamacare regulations? Still here. Taxes? Most still in place, totaling hundreds of billins of dollars. Insurance company bailouts? Those, too.

Paul bashed the bill's inclusion of a stability fund of nearly $200 billion to help prop up Obamacare exchanges on the individual market, which is primarily used by people that don't get insurance via work.

Paul also railed against using tax credits to pay down the cost of insurance, much like Obamacare now, and keeping around cost-sharing subsidies to insurers for two years.

Paul has been a staunch opponent of the Senate bill since it was unveiled last month. He joined three other conservative senators — Ted Cruz of Texas, Mike Lee of Utah and Ron Johnson of Wisconsin — to oppose it hours after it was released.

Cruz and Lee have been working with Senate leadership on an amendment to get their support. The amendment would allow insurers to sell plans that don't meet Obamacare's insurer mandates as long as it sells a plan that does.

The amendment is now being evaluated by the Congressional Budget Office to determine its impact on spending and insurance coverage. Cruz and Lee have indicated that including the amendment is vital to get their support.

Paul did not mention the Cruz amendment in his op-ed.