The Brexit department has apologised after David Davis made a surprise visit to the Irish border.
The Brexit Secretary spent two hours near the border in Northern Ireland on Monday, but the trip drew criticism from Sinn Fein because the area's local MP was not informed.
Mickey Brady, MP for Newry and Armagh, accused Mr Davis of avoiding a meeting with him because he is "afraid to face the truth about Brexit".
A spokeswoman for the Government's Department for Exiting the European Union said of the lack of notification: "This was an administrative oversight for which we are happy to apologise."
The DUP were not given notice of the trip either but the spokeswoman said the Northern Ireland Office had been informed ahead of the visit.
Mr Brady's party colleague, West Belfast MP Paul Maskey, said Mr Davis had shown "contempt" for local politicians and not followed protocol in arranging the visit.
He tweeted: "Out of courtesy and protocol he should have informed you (Mickey Brady) as the local MP.
"Shows his contempt to locally elected representatives who know more about the impacts of Brexit than he will ever know."
Out of courtesy and protocol he should have informed you as the local MP. Shows his contempt to locally elected representatives who know more about the impacts of Brexit than he will ever know. https://t.co/2Emie6oe1A— Paul Maskey (@PaulMaskeyMP) April 23, 2018
The trip, made almost two years after the EU referendum, was little more than a "box-ticking exercise", the SDLP's Claire Hanna said.
The South Belfast MLA, who is the party's spokeswoman on Brexit, said Mr Davis should have been open to addressing local concerns during the visit.
She said: "Maybe the minister is troubled that we might actually have asked him if he learned anything and how he plans to stop a hard border here when his Government continues to dig its heels in on the customs union.
"This visit was nothing more than a box-ticking exercise. The border shouldn't have just been an afterthought months down the line but should have been a priority for the Brexit Minister."
Following the short trip, during which Mr Davis was escorted by former senior police officer and Cooperation Ireland chief executive Peter Sheridan, he reiterated the Government's determination to avoid a hard border on the island.
Mr Davis tweeted: "As we leave the EU it's essential both the UK and EU do what it takes to keep the border, which I saw this morning, free from physical infrastructure.
"We are determined to get this agreed by October."
Today I started what promises to be a busy week in Northern Ireland. As we leave the EU it's essential both the UK and EU do what it takes to keep the border, which I saw this morning, free from physical infrastructure. We are determined to get this agreed by October. pic.twitter.com/W4zSuRSGRG— David Davis (@DavidDavisMP) April 23, 2018
As part of the trip Mr Davis visited an autism centre in Middletown in Co Armagh as well as a nearby food processing company.
He also saw a former customs post between counties Armagh and Monaghan.