She also appointed Justice Minister David Lidington to the post of Cabinet Office minister, filling the job responsible for the administration of the government.
Around 20 minutes later Mr Lewis was seen entering Number 10 and within an hour he was announced as party chairman and minister without portfolio. The reshuffle began when the Conservative Party's social media team tweeted congratulations to Transport Secretary Chris Grayling on his appointment as the new Conservative Party chairman.
Conservative staff reportedly tweeted the false news on the basis of media speculation.
Earlier, BBC political Laura Kuenssberg mentioned (though with an unconfirmed caveat) that Chris Grayling was set to be the new chairman - in which she later tweeted that it should be Brandon Lewis instead according to her sources.
His appointment was nearly derailed after the party was forced to delete a tweet congratulating Transport Minister Chris Grayling on his promotion to the position, which members say has become increasingly important.
THERESA MAY ordered a total overhaul of the Tories busted war machine with a burst of new blood in key party roles.
Iran says to reconsider cooperation with IAEA if USA dishonors commitments
Under the deal, Iran is obliged to put restrictions on its nuclear activities in exchange for termination of economic and financial sanctions.
Those expected to be sacked include party chairman Patrick McLoughlin, education minister Justine Greening and May's leadership rival, Andrea Leadsom, who is leader of the house.
"Clearly, she's keen to put her stamp on the party and do the things you try to do with reshuffles - bring through new talent, make the party more representative - but she's very constrained", Rob Ford, a professor of political science at the University of Manchester, said of May's decisions.
Sir Patrick McLoughlin, a minister as far back as the Thatcher government, could be replaced having overseen the general election campaign that ended with the Tories losing their majority.
The reshuffle was sparked in part by the resignation of May's ally, Damian Green as the de-facto deputy prime minister, after police who were investigating a separate matter revealed they had found thousands of pornographic images on his computer.
Braintree MP James Cleverly has been appointed deputy chairman, No 10 also confirmed.
Changes to the junior ministry will take place on Tuesday, London time.