The credit ratings agency said the rating outlook remained negative, as it cut Carlton's long-term debt rating to Baa3 from Baa2 and the company's short-term to Prime-3 from Prime-2.
Moody's said the downgrade was based on the negative impact on Carlton's core cash flows and the continued weakness in TV advertising market.
Last month, Carlton reported half-year pre-tax losses fell to £179.4m and that advertising revenues were down 13% in the six months to March 31.
The loss includes a £99m exceptional charge resulting from the closure of ITV Digital and ITV Sport. However, Carlton did say that it was seeing signs of a recovery in the second half.
Shares have fallen steadily since last month. When Carlton reported its interim results on May 28 its share price stood at 263.25p. This afternoon they fell by 0.48% to trade at 214p.
Moody's also said that the downgrade took account of the structural challenges facing ITV in holding on to its market. The downgrade coincided with new figures from Barb, which showed that ITV1's audience share had fallen from 46.6% to 39%.
The credit rating agency said the negative outlook reflected ongoing uncertainties about the prospect of a recovery in the TV advertising market and the as-yet-uncertain outcome of the ITV Digital legal case, which could result in Carlton and ITV Digital partner Granada paying the Football League as much as £500m.
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