Brent fell over 2 percent to $51.10 a barrel by 10:00 a.m. to a price not seen since the end of January.
U.S. crude, meanwhile, fell 68 cents to $46.43 a barrel after hitting its lowest in four months at $46.35 a barrel. However, it was still off its March low which saw the commodity dip below $43 a barrel.
Barclays oil analyst Miswin Mahesh told CNBC Monday that a number of factors had coincided to inevitably lead to a price decline, but remained upbeat on the price over the longer term.
"As much as things are looking weak at the moment, I think the price in itself would be a catalyst to tighten market balances come 2016," he said.
Barclays expect Brent to rebound to $66 a barrel by the second quarter of 2016 and WTI to reach $63 a barrel.
Analysts have highlighted a raft of reasons for the latest fall with several data points weighing heavily on Monday morning.