She said computer systems to handle new customs requirements were only likely to be in place in December, leaving companies to deal with training staff while heading into the festive period.
And she warned even if a deal was reached, increased paperwork and delays would still impact businesses.
She said: “The whole point of the transition period was there would have been a deal agreed more than a year ago back in March 2019 and you would have a year and a half to develop and train and put in place all the bits for the January 1.
“Here we are five weeks away and there isn’t even a deal. It is irresponsible and particularly in the middle of the Covid crisis. They keep saying how dare we talk about independence when there is a Covid crisis – yet they are ploughing ahead with Brexit.”
Time is fast running out for the UK and EU to reach a deal before the Brexit transition arrangement expires at the end of this year.
Talks last Thursday faced a setback after face-to-face negotiations were temporarily suspended when a member of Michel Barnier’s team tested positive for Covid-19. And EU leaders were urged to step up contingency plans for a No-Deal Brexit at a virtual summit.
On Friday, there was cautious optimism when European Commission president Ursula von der Leyen said there had been “more movement” on important issues.
But she said “time pressure is high”, with three main outstanding issues on fisheries, state aid rules and governance arrangements still to be resolved.
The Prime Minister’s official spokesperson said the Government still wanted to get an agreement “as quickly or as soon as possible”.
However Whitford said: “A lot of the delays, the bureaucracy and the increased paperwork, that’s going to happen anyway.
“If you have a deal, you at least don’t have tariffs on top of that.”
Whitford, who is a member of the House of Commons Select Committee on the Future Relationship with the European Union, said it had heard concerns last week from farming, retail and manufacture representatives in Northern Ireland over the lack of preparedness.
She said the UK Government needed to outline what the plan is so businesses know what to prepare for and get IT systems in place.
She added: “There will be many businesses who don’t realise what their connection is to Europe – they don’t export and don’t recognise that something they use starts life in Europe.
“They might go I’m just a wee hairdresser, it’s nothing to me – but where do your products come from? There will be lots of people quite far down the supply chain.”
Meanwhile, the UK and Canada have agreed a deal to continue trading under the same terms as the current European Union agreement after the Brexit transition period ends, in a relief for businesses fearing high tariffs.
A new comprehensive deal with Canada had been touted as one of the benefits for the UK leaving the bloc – but this arrangement will not yet bring any additional advantages for businesses.
The Government said the agreement would pave the way for negotiations to begin next year.
Prime Minister Boris Johnson and Canadian counterpart Justin Trudeau sealed the “agreement in principle” in a video call yesterday.
It rolls over the settlement agreed by the EU with Canada in the Comprehensive Economic and Trade Agreement (Ceta).
The Department for International Trade (DIT ) said it avoids an estimated £42 million of tariffs exporters in the UK would have faced if the Government had failed to get a deal.
Industry groups expressed relief that businesses will not face higher trade tariffs with Canada next month.
Federation of Small Businesses chairman Mike Cherry said: “There was always a danger that the end of the transition period would mean losing wider international market access that we enjoyed as part of EU membership.”