The resolution was passed in plenary by an overwhelming majority, 615 votes to just five against.
The move comes in response to numerous scandals that have hit sitting and former Commissioners.
The vote also comes amid fresh 'revolving door' allegations against Neelie Kroes, a former Vice President of the Commission, as well as the ongoing controversy surrounding former Commission President José Manuel Barroso who led the executive for two terms.
MEPs want tougher disclosure rules on Commissioners' declarations of interests. The resolution also says the Commission should revise its code of conduct "to ensure that their declarations of interests give a complete picture of the financial situation and activities of a Commissioner and his or her family."
MEPs advocate prolonging the 'cooling off' period, before ex-commissioners may take private sector jobs in their areas of expertise, from the current 18 months to at least 36 months.
Commission President Jean-Claude Juncker recently proposed 24 months for ex-Commissioners, and 36 months for a Commission President.
Transparency campaigners have said that these proposals are "totally inadequate."
In addition, the declaration of financial interests, according to the parliamentary resolution, must include present or past interests or activities from the last two years.
MEPs recommend that Commissioners should declare all their interests as "shareholders, company board members, advisors and consultants, members of associated foundations", as well as close family interests and changes that took place when their candidatures were made known.
In the event of a conflict of interest being identified while in office, the Commission President should follow Parliament's recommendations for resolving the conflict or Parliament may recommend withdrawing confidence in that Commissioner and, when appropriate, deprive him or her of the rights to a pension and other benefits, says the text.
MEPs also called for a bigger role for Parliament's legal affairs committee in analysing the declarations of financial interests, verifying that they have been duly completed with the right content and assessing whether a conflict of interest may be inferred.
Clearance from this committee on the absence of any conflict of interest should be a precondition for holding the hearing of a Commissioner-designate by the committee responsible for his/her future portfolio, says the resolution.
MEPs stress that the legal affairs committee should be able to determine that a Commissioner should either renounce certain financial interests or that changes should be made in his or her portfolio.
Adoption of the resolution comes amid potentially damaging fresh allegations against Kroes, who reportedly provided a letter to the at-the-time Commission President-elect, Barroso, ruling out business activity after her term as Commissioner.
It has also been claimed that other documents from 2004 relating to handling her potential conflicts of interest have been "lost" by the Commission.
After leaving her Commission post, Kroes, formerly in charge of the digital agenda, went on to become a special adviser to Bank of America Merrill Lynch in 2014 and in 2016 joined the public policy advisory board at Uber and became a director at Salesforce.com.
Barroso, meanwhile, still finds himself at the centre of a storm over his appointment to a top job with Goldman Sachs.
GUE/NGL MEP Kostas Chrysogonos said that a revision of the code of conduct is necessary to "ensure that Commissioners are able to fulfil their mandates independently and to ensure maximum transparency and accountability."
The Greek deputy said, "The central premise of the proposals is that the Commissioners' declarations of interests should be more thorough and rigorous. This is absolutely necessary to protect the credibility of the EU.
"This issue is especially important after a series of incidents, such as the appointment of Barroso to a key post in the banking sector, that show the possibility of conflicts of interests between public servants and the private sector."
Further reaction came from Tadeusz Zwiefka, a Vice-Chair of Parliament's EPP group, who said, "The college of Commissioners is a group of top EU officials.
"It is not surprising that any information about Commissioner activity outside his or her mandate provokes strong emotions among both national politicians and EU citizens. This is why it is so important that the commissioners do not raise any suspicion of conflict of interest."
He stressed, "The irreproachable conduct of the Commissioners is important not only for their personal image, but for the image of the EU as a whole.
"The recent revelations about the activities of some former Commissioners not only hamper the image of the Commission but that of the whole EU becoming the munition for the EU's opponents."
Zwiefka added that under the resolution adopted this week, the legal affairs committee would have more "certitude" when it comes to the verification of any possible conflicts of interest.
He said, "This was Parliament's task: now it's up to the Commission to fulfil its own commitments and adequately revise the code of conduct for Commissioners."