The health regulator has been forced to step in after a hospital “persistently” failed to treat emergency patients within four hours.
Monitor said it was also taking action against Kettering General Hospital NHS Foundation Trust because of its "board governance and financial performance".
The hospital, which provides services for 300,000 people in north Northamptonshire, achieved Foundation Trust status - a supposed marker of excellence in the health service - in 2008.
Monitor, which regulates foundation trusts, said Kettering General Hospital was in "significant breach" of the terms of its authorisation.
The regulator has ordered the trust to improve its accident and emergency performance, take "rapid action" to strengthen its financial plan for 2012/13 and to have a review of its board governance.
Monitor's chief operating officer, Stephen Hay, said: "We have been tracking the trust's performance for some time and are requiring action to be taken because it is not acceptable that the trust is persistently failing its A and E patients. We now expect the trust to focus on immediately and sustainably resolving this issue.
"We require the trust to scope out a review of its board's governance and immediately improve its 2012/13 financial plan to deliver effective cost savings. As part of this, the trust needs to get to grips with its cashflow."
Kettering General Hospital Foundation Trust chairman Steve Hone said: "This year we have had difficulty in terms of two targets. One is the national target of admitting or discharging 95% of A&E patients within four hours of arrival in the department.
"The second is in terms of maintaining a financial trajectory that will mean we end the financial year with a surplus - a requirement for Foundation Trusts.
"Progress has been made on A&E and the good news is that, over the last three months, July-September, our performance has risen above 95% and we have put a lot of work into developing more robust systems that enable us to maintain this."
He continued: "However, Monitor does feel we need to do more in order to achieve our targets consistently and to prove that we have strong systems of governance in place to monitor them.
"Therefore they have asked us to develop and implement a robust action plan to maintain our A&E performance, take rapid action to improve our finances and to commission an agreed review into the way we make decisions and monitor our performance.
"We will be meeting monthly with Monitor to review our progress in these matters until we have demonstrated that the issues are resolved.
"Patients and staff should be reassured that the hospital is continuing to perform well across the rest of our business."