Morning top 5: UK to trigger Article 50; Justice Minister defends Garda Commissioner

The top stories this Wednesday morning...

The British Prime Minister says she is "determined to seize this historic opportunity" as she officially starts the process of leaving the EU later.

Theresa May will trigger Article 50 - giving her two years to reach a Brexit deal with Europe.

She says it's "one of the most significant moments the UK has faced for many years".

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Mrs May has already signed the letter invoking Article 50 and it will be hand delivered to European Council President Donald Tusk later.

Around the same time she will address parliament on the issue, and after that the clock starts ticking on two years of Brexit deal negotiations.

In the coming days the EU's negotiating guidelines will be given to Taoiseach Enda Kenny and the other leaders of the remaining member states, laying the ground rules for the talks to come.

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The Justice Minister has strongly defended the Garda Commissioner in the face of continuing opposition calls for her to step down.

Frances Fitzgerald says an independent external investigation must find out if the controversies surrounding breath tests and speeding convictions were the result of carelessness or collusion.

In the Dáil last night, she said Commissioner Nóirín O'Sullivan is the best person to lead the force.

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There are new calls for the Transport Minister to intervene amid fears the Bus Éireann strike could spread to Irish Rail and Dublin Bus.

SIPTU has warned it will ballot its CIE members to strike in solidarity with their colleagues after indications Bus Éireann may be considering compulsory job losses.

Workers from across the sector are staging a lunchtime protest today to coincide with the appearance of Shane Ross at the Oireachtas Transport Committee.

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The US President has signed an executive order restricting the US government's power to enforce environmental regulations.

Campaigners are worried about how it will impact efforts to tackle climate change, and more than a dozen US states say they will fight it in court.

However, Donald Trump insists it will help to protect American jobs in the coal industry.