The chair of parliament's ethics watchdog has said MPs should be forced to exercise more "due diligence" over donations, in response to Sky News' Westminster Accounts project.
Sky News and Tortoise Media have launched a new database of MPs' second jobs and donations - the first time they have all been collated in one place.
MPs have been accused of failing to provide "sufficient" transparency after our investigation struggled to uncover basic details about who is behind major donations.
Among the top donors to individual politicians are companies where little detail was provided in the MPs' declarations about who they are, who is in charge and where they are based.
Speaking to Sky's deputy political editor Sam Coates, Lord Pickles said MPs should have to know and declare a named individual as the originator of a donation, even if the funds come from a company.
"It wouldn't take very much to just to sort this out," said Lord Pickles, who is the chair of the Advisory Committee on Business Appointments.
"There is a degree of due diligence that members of Parliament are not required currently to do under the rules, but basically should be, which is pretty straightforward, which is 'why is this organisation giving me money and do they expect anything in return'?"
Lord Pickles said it "wouldn't be unreasonable to put together some guidelines for MPs to be able to answer some just very basic questions".
"It doesn't mean to say they have to do a line-by-line scrutiny of the company or employ expensive accountants to do so, but to be able to answer just one or two questions like who has given this money and who is the controlling thought behind that company and why they're doing it.
"And just to simply say this money is to be used for this, there are no restrictions. Or this is to conduct research in a particular area. This isn't actually going to put an enormous burden on members of parliament, and I think it will remove an awful lot of worry."
Sky's Westminster Accounts investigation has discovered that nobody had heard of a company donating hundreds of thousands to Labour MPs on a visit to its registered address, while the office of another company that donates to 24 Tory MPs was shut and apparently out of action.
When asked for comment, some of the MPs concerned were reluctant to discuss the details until after the stories were published.
Lord Pickles said there "isn't enough transparency" and it "wouldn't take a big effort" to improve this.
Praising the Westminster Accounts project he said: "I've loved what you've been doing.
"I've played around with the toolkit that you've provided. I would have thought from even the casual observer that you've not demonstrated or attempted to suggest there's something sleazy about this.
"All you've suggested is that there should be a degree of transparency as to why the money is needed."
Westminster Accounts has also thrust the issue of MPs second jobs back into the spotlight.
Media appearances 'grey area'
There have been calls for the rules to be tightened on outside earnings since the Owen Patterson lobbying scandal, which saw Tory MPs attempt to save a colleague who broke lobbing rules from punishment.
During an interview with political editor Beth Rigby, Labour's deputy leader Angela Rayner said being an MP is "a full time job" but earning money through media appearances and speeches is a "grey area".
This has enabled figures like former PM Boris Johnson, and Shadow Foreign Secretary David Lammy to make thousands on top of their MPs salary.
Ms Rayner said an independent ethics commission should rule if MPs should be allowed to do this in future.
"It's not just about how much you earn from it, it's actually about how does that contribute to your job as an MP and to public life as a politician," she said.
"You know, making huge amounts of money off things that don't actually represent your constituents I think is a different matter. But I don't think it's for me to decide, that this is why we would set up an independent ethics commission that looks at these things."
Sir Ed Davey, the leader of the Liberal Democrats, said that MPs who are "earning £300,000 for an hour's speech" should "seriously look at themselves and the rules need to be tightened up on that".
He added: "One reason I welcome what you are doing on Tortoise is I want to have that debate again. I want to clean up British politics, I want tighter rules and I want to transform party finances."