Patients at Wishaw General were diverted to other hospitals at the weekend as the A&E department struggled to cope with demand.
The hospital opted to send patients to nearby Monklands for a period of time on Sunday due bed shortages although hospital chiefs maintain the A&E department remained open.
The health board's director for acute services, Judith Park, told Lanarkshire Live : “We had diversions in place for a period of time yesterday due to significantly high levels of activity and bed shortages at the site.
“Our A&E department remained open and we continued to see patients.
“When we experience an exceptionally high rate of emergency admissions, we work as a clinical network to divert some patients to another NHS Lanarkshire hospital where it is clinically appropriately to do so.
“The sustained pressure we are seeing across our three acute hospitals is showing no signs of easing.
“We continue to see exceptionally high numbers of people attend A&E, including many who attend for conditions that would be best treated elsewhere.
“We are asking people to please keep our A&E departments safe for those who need critical care.
“If you think you need to attend A&E but it’s not life-threatening, you should consider the alternatives.
“You can call NHS 24 on 111 day or night, where you will be directed to the right NHS service. If you just need health care advice, then please use the NHS Inform website.”
The news of the closure comes as one Lanarkshire MSP called on the Health Secretary to step in to help the situation.
Meghan Gallacher’s call comes after A&E waiting times in NHS Lanarkshire remained at under 70 per cent of patients being seen within four hours.
The target is 95 per cent.
Wishaw is recording that on 61.8 per cent of patients were seen within four hours.
Ms Gallacher said: “These latest A&E figures are very worrying.
"Recently, NHS Lanarkshire were left with little option but to announce a ‘code black’, the most serious level of pressure.
“Humza Yousaf has failed to get on top of this crisis and more and more patients are paying the price.
“Our heroic frontline staff are working flat out in NHS Lanarkshire but they are under an intolerable strain and they haven’t been fully resourced by Humza Yousaf.
“In July, Humza Yousaf said that it was “misleading” to suggest the NHS was on the verge of collapse.
"The fact that a ‘code black’ has been declared, the British Army has been called in, targets are being missed, and there is a very real threat of strike action from our overworked nurses.
“All of these indicates that there is a crisis and Humza Yousaf is clearly out of his depth. Therefore, I am urging the First Minister to step in to resolve these issue immediately.”
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