The IPA Bellwether, conducted by IHS Markit, and based on a questionnaire survey of around 300 UK-based companies, stuck to its forecast and said it remains cautious towards 2019. It expects a 1.1% annual increase in ad-spend over the year.

"Nevertheless, it (the Bellwether report) believes businesses will be eager to accelerate marketing efforts once uncertainty has cleared, and subsequently sees 2020 onwards being more positive on the ad-spend front," the survey said.

It expects growth of 1.8% in 2020, followed by stronger rates of increase in the years after that.

Bellwether panel members, recruited from Britain's top 1,000 companies, said the underwhelming performance of marketing budgets continued into the quarter and that the net balance was broadly unchanged from the prior quarter.

"Low consumer confidence was said to have generated hesitancy towards spending, leading firms to hold back on big-ticket marketing drives and tighten the purse strings," the survey said.

Britain is scheduled to leave the European Union on Oct. 31, but it is still uncertain whether the two sides can make a breakthrough over the terms of the departure, while the risk of a disorderly no-deal Brexit also remains.

The survey showed that development of new online tools encouraged firms to boost their internet budgets with internet marketing remaining the "top performer" in the third-quarter.

The report comes as advertising companies, including market leader WPP Plc, are seeing clients switch to online platforms such as Google and Facebook to reach consumers.

Industry forecaster Zenith had said earlier this month ad spending on social media is expected to grow 20% in 2019, overtaking print to become the third-largest advertising channel.

(Reporting by Tanishaa Nadkar in Bengaluru; Editing by Shailesh Kuber)