Smith was made Secretary of State for Northern Ireland when Boris Johnson assumed the role of Prime Minister. Under his tenure devolved power-sharing was restored in January 2020. Smith was sacked as Northern Ireland Secretary in Johnson's post-Brexit reshuffle. He had lasted 204 days in the role. The decision to dismiss Smith as Northern Ireland Secretary was criticised by a number of prominent political figures in Northern Ireland, including SDLP leader Colum Eastwood who described the move as showing "dangerous indifference" by the Prime Minister. Smith had been widely seen as instrumental in securing a cross-party deal to restore the Northern Ireland Executive, after three years without a devolved government in Stormont. Tributes to Smith's tenure as Northern Ireland Secretary were paid by NI First MinisterArlene Foster and TaoiseachLeo Varadkar. Both praised him for his role in ending the political deadlock in the country. Many political commentators expressed their surprise at Smith's dismissal, given his perceived success during his time as Secretary of State for Northern Ireland. Some suggested that Smith's testimony to the Northern Ireland Affairs Select Committee in October 2019, in which he described a potential no-deal Brexit as being "a very, very bad idea for Northern Ireland", had influenced the decision to remove him from his position. Stephen Bush, political editor of the New Statesman, speculated that the consequence of Johnson's removal of Smith would be the destabilisation of the new power-sharing agreement and increased difficulty in negotiating the details of the "New Protocol".
Security
In October 2013 The Guardian alleged that Smith may have breached national security by posting an image on his website of himself alongside military personnel. Smith had previously asked questions in Parliament about whether The Guardians handling of intelligence material leaked by Edward Snowden had breached national security. He reported the newspaper to the police. Smith argued the newspaper should be investigated as it had "endangered" British security personnel by publishing leaked information.
Pairing allegations
On 19 July 2018, Smith was reported to be resisting calls to resign his position as Government Chief Whip, following allegations that he had instructed five Conservative MPs to break "pairing" agreements in an important parliamentary vote the previous day. Only one MP, Conservative party chairman Brandon Lewis, complied with the instruction. Subsequent reports indicated that Smith had given similar instructions to five MPs, but Lewis had been the only one willing to break what one commentator described later as "a centuries old ‘code of honour’". Before it became known that the affair had involved approaches by Smith to more than one MP, the Prime Minister Theresa May backed Lewis by stating that "The breaking of the pair was done in error. It wasn't good enough and will not be repeated."