Sen. Elizabeth Warren will announce a plan Thursday to limit the influence of lobbyists and contractors on the Department of Defense, according to sources close to the Massachusetts Democrat and 2020 presidential candidate.

Dubbed the Department of Defense Ethics and Anti-Corruption Act, the new proposal would impose a four-year ban on large defense contractors hiring top Defense Department officials, prohibit top Defense Department officials from owning stock in major defense contractors, require contractors to submit records of their lobbying activities and prohibit some former senior government officials from working for foreign entities without explicit approval by the Secretary of State.

According to the Project on Government Oversight, a nonpartisan government watchdog group, the top 20 defense contractors—like Boeing and Lockheed Martin—hired more than 600 former senior government officials, top military officers, Congressional leaders and senior legislative staff in 2018 alone. Warren argues it shouldn’t be easy to transition from working for a government agency that buys contractor materials to working for a major company that sells contractor materials to a government agency.

“These giant contractors have deployed an extremely profitable strategy: recruit armies of lobbyists from former Pentagon officials and congressional staffers who stream through the revolving door. Then, get those former officials to use their relationships and access to influence our country’s national security apparatus,” Warren, a member of the Senate Armed Services Committee, wrote in a Medium post published Thursday morning. “We have to call this what it is: corruption, plain and simple.”Warren also says it’s time the Defense Department sees a budget reduction.

In Fiscal Year 2017, approximately 15% of the federal government budget, or $611 billion, went to defense-related activities, according to an analysis by the Center for Budget and Policy Priorities. Meanwhile, that same year, about 9% went to economic relief programs like food stamps, unemployment insurance and Supplemental Security Income for the elderly or disabled poor.

“It’s unsustainable,” Warren writes. “And it’s bad for our national security. If more money for the Pentagon could solve our security challenges, we would have solved them by now.”

Notably, Warren was one of seven Democrats to vote against the the senate confirmation of Acting Secretary of Defense Patrick Shanahan when he was up for the Deputy Defense Secretary gig, in part, because he was a former executive at Boeing.

She also requested that the Pentagon watchdog unit look into whether Shanahan used his position to influence the Pentagon’s relationship with Boeing. In April the Department of Defense Office of Inspector General said it could “not substantiate any of the allegations,” clearing the way for President Donald Trump to formally nominate him to the top job.

“His obvious potential conflicts of interest remain,” Warren writes. “The truth is that our existing laws are far too weak to effectively limit the undue influence of giant military contractors at the Department of Defense.”

Since Warren announced she was running for president in February, she’s put out a slew of policy plans, including granting extremely low-income families free childcare, erasing student loan debt shouldered by millions of Americans, rewarding hospitals that would make childbirth safer for African-American women and addressing the opioid crisis in America.

Warren recently authored a separate piece on Medium that detailed her plans to involve the military in climate change prevention. In it, she says she’d ask contractors that have not achieved net zero carbon emissions to pay 1% of their total contract values, and that these fees would be invested in modernizing military infrastructure.

Write to Abby Vesoulis at abby.vesoulis@time.com.