The collapse of MG Rover and the knock-on effect hitting its suppliers pushed the flow of new orders, particularly export orders, for British industry as a whole into reverse last month for the first time in two years.
The shortfall had the effect of lowering the overall purchasing managers index for manufacturing activity narrowly into negative territory after nearly two years of unbroken growth.
On a measure where 50 represents no change, anything above is growth and anything less a decline, the index dipped to 49.5 from 51.6 in March.
Output, though, continued to grow. But the Chartered Institute of Purchasing and Supply, which publishes the PMI with NTC Research, noted that this growth was sustained by work on contracts agreed in earlier months.
Birmingham Chamber of Commerce and Industry stated that these findings under-scored its plea for whatever political party is elected tomorrow to incentivise manufacturing to invest.
"With a company the size of MG Rover collapsing and the effect that has had on the automotive supply chain, these figures come as no surprise," said Jerry Blackett, the chamber's policy director.
"What we need to ensure now is that there is a concerted effort to aid manufacturers, whether this comes in the guise of interest rate cuts, tax breaks or other forms of support that can allow our firms to compete with foreign competitors."
The Black Country Chamber echoed that with a call for no more interest rate increases.
" We have suffered enough recently with the impact of the Rover collapse on the supply chain and all the uncertainty connected with the General Election," said Ian Brough, chief executive.
Two members of the Bank of England ' s interest-setting Monetary Policy Committee voted to raise the cost of borrowing last month. "That attitude must not be allowed to gather any more momentum," Mr Brough added.
Roy Ayliffe, director of professional practice at the CIPS, noted: "The deterioration was linked mainly to declining levels of new business, which fell after two years of growth."
Exports also fell for the fourth consecutive month as demand from key eurozone markets dwindled and competition from East Asia increased, he continued.
The PMI's manufacturing employment index, which had risen slightly in March, was squeezed back to 47.3 by cost-cutting measures as well slower growth. High oil, steel and plastic prices continued to drive up industry's costs, but not as quickly as in recent months. The input price index fell to its lowest level since February, 2004 at 62.5.
Manufacturers succeeded in passing more of these increases on to their customers, though still not enough to maintain their margins. The index measuring their output prices picked up to a faster, although still modest, pace, rising to 51.6 from 50.9 in March. New export orders eased for the fourth straight month at 49.2, mainly due to stronger competition from China and Japan.