Brian Williams was reprimanded by his boss at MSNBC for 'patronizing' host Rachel Maddow by thanking her for 'visiting' his newscast even though he had taken over her nightly time slot to report on the US missile strike in Syria earlier this month, it was claimed on Saturday.

Sources at the liberal-leaning cable news outlet said that Phil Griffin, the president of MSNBC, 'gave Brian a very stern rebuke, telling him "Don't you ever do that again",' according to Page Six.

The former NBC Nightly News anchor was summoned to steer MSNBC's coverage of the US Navy's Tomahawk missile strike on Syria, which President Donald Trump ordered after the regime of President Bashar Assad was blamed for an attack on civilians with chemical weapons.

The coverage broke into Maddow's nightly program, The Rachel Maddow Show, which has generated significantly higher ratings in recent months.

Brian Williams (left) was reprimanded by his boss at MSNBC, Phil Griffin (right), for 'patronizing' host Rachel Maddow by thanking her for 'visiting' his newscast even though he had taken over her nightly time slot to report on the US missile strike in Syria earlier this month

Williams steered coverage of the Syria strike on April 6, which broke into Maddow's (above) nightly program, The Rachel Maddow Show

Williams' anchoring of the April 6 broadcast has been widely panned by critics who not only objected to his perceived intrusion on Maddow's turf, but also because he repeated his observation that the video footage of the missiles being launched was 'beautiful.'

'Not only did Brian go way over the top with his coverage of the missile strike,' an MSNBC source told Page Six.

'He then totally patronized Rachel by thanking her for 'visiting' her own show and being 'a part' of his 'beautiful' coverage! Has he not learned anything from 'Misremember-gate'?'

'Misremember-gate' refers to statements made by Williams in which he exaggerated claims of coming under fire while reporting from war zones in Iraq.

Williams would later claim in an interview with Stars and Stripes that he 'misremembered' certain details of his experiences covering the 2003 invasion of Iraq.

Williams' anchoring of the April 6 broadcast has been widely panned by critics who not only objected to his perceived intrusion on Maddow's turf, but also because he repeated his observation that the video footage of the missiles being launched (above) was 'beautiful'

The controversy, which erupted in February 2015, generated an intense backlash and forced NBC News to remove Williams from anchoring the nightly newscast.

After a six-month suspension, Williams returned to the air on MSNBC in September 2015.

His broadcast in place of Maddow to cover the breaking news from the Middle East angered fans of TRMS, who said MSNBC's decision was 'sexist.'

Viewers also took issue with some of Williams' comments on the broadcast, especially when he played videos of the missiles being launched and said: 'We see these beautiful pictures at night from the decks of these two US Navy vessels...

'I am tempted to quote the great Leonard Cohen, "I am guided by the beauty of our weapons".

'And they are beautiful pictures of fearsome armaments making what is for them a brief flight over this airfield.'

Despite the backlash from both fans and network executives, Maddow 'didn't seem bothered by it and just laughed it off,' according to Page Six.