"But this can not be at the expense of transparency, fairness and compliance with the law", ICO's information commissioner, Elizabeth Denham, said in a statement. "But this can not be at the expense of transparency, fairness and compliance with the law".
Cambridge Analytica, a London firm financed by wealthy Republican donors, worked for the 2016 Trump campaign and for a while employed Steve Bannon, the Trump campaign CEO and later a White House adviser.
Collins said Wednesday that the social media giant "should now make the results of their internal investigations known to the ICO, our committee and other relevant investigatory authorities".
Facebook said apps developed by the Russian technology conglomerate Mail.Ru Group, were being looked at as part of the company's wider investigation into the misuse of Facebook user data, CNN reported.
"A significant finding of the ICO investigation is the conclusion that Facebook has not been sufficiently transparent to enable users to understand how and why they might be targeted by a political party or campaign", Denham wrote, according to the Post.
The final decision regarding the fine will be made after Facebook issues a response to the notice.
"Facebook users will be rightly concerned that the company left their data far too vulnerable to being collected without their consent by developers working on behalf of companies like Cambridge Analytica. Trust and confidence in the integrity of our democratic processes risk being disrupted because the average voter has little idea of what is going on behind the scenes", Denham said.
The UK's data protection watchdog said the social media giant has failed to ensure Cambridge Analytica had deleted users' data.
Despite the proposed fine being a record for the watchdog, campaigners said it was "unacceptable", as under new data laws the penalty could have totalled more than £450 million. "People can not have control over their own data if they don't know or understand how it is being used".
The ICO's probe into whether political parties had used data manipulate the populous in the Brexit referendum was launched in March 2017, and later extended that to cover data analytics firms, data brokers and social media platforms.
"We must change this fast as no-one should win elections using illegally obtained data", she said, adding: "We will now assess what can we do at the European Union level to make political advertising more transparent and our elections more secure".
"This can not by left to a secret internal investigation at Facebook".
The next phase of the ICO's work is expected to be concluded by the end of October.
Facebook has said it will be reviewing the report and responding to the ICO soon.
Facebook could face a hefty compensation bill in Australia after a leading litigation funder lodged a complaint with the country's privacy regulator over users' personal data shared with a British political consultancy.